Let's look back at each Mario RPG, where it came from, and what it offered.
Super Mario RPG
A joint effort between Nintendo and Squaresoft, the RPG giant of its time, SMRPG began the unlikely marriage between the red plumber, stats, and storyline. This title introduced the action combat system that every future Mario RPG would build on, requiring timed button presses to attack or defend with more efficiency. Perhaps the most unique aspect of SMRPG is in its ousting of Bowser as the main villain, instead introducing Squaresoft's own gang of baddies: The Smithy Gang, a group of interstellar hooligans bent on conquering the Mushroom Kingdom.
While the story was still relatively simple compared to standard RPGs, it really shone in its fusion of the standard "quest to save the world" that grandiose games such as Final Fantasy were known for and the traditional Mario charm of the mainline Mario games. The script relied heavily on humor and a unique brand of quirkiness, but never shunned its purpose to deliver a story centric Mario game: you felt the presence of the Smithy Gang in each area of the Mushroom Kingdom that you visited, and their omnipresence created a sense of urgency that the world needed to be saved. Another staple that SMRPG introduced was the gathering of seven stars, which would later be repeated in Paper Mario and The Thousand Year Door.
While it began as Super Mario RPG 2, with incessant promises from Nintendo Power that the graphics "weren't finished yet", Paper Mario eventually embraced its paper aesthetic and created a franchise of its own. Squaresoft had fallen into disagreement with Nintendo for various reasons, so this next entry in the RPG series was left to Intelligent Systems, the developer of the Famicom/Advance Wars and Fire Emblem series. Paper Mario built heavily on its predecessor, but left behind a bit of the standard RPG flair that Square had injected into SMRPG in favor of a more simplistic Mario-esque flavor.
Hit points and flower points were drastically scaled down, and the battle system was retooled to accommodate Mario as its primary player, with partner characters being limited to one at a time. This time around, however, partners had uses outside of battle, leading to more emphasis on light puzzle solving than in SMRPG. The biggest change between the two titles was, of course, the graphical style, with Paper Mario abandoning the isometric view for a two dimensional side view. The story was less "epic" and Final Fantasy-esque, but one could argue that it contained much more whimsy and charm as a substitute.
Paper Mario: The Thousand Year Door
A direct, by the numbers sequel to Paper Mario 64, TTYD left the Mushroom Kingdom for the unique setting of Rogueport. Unlike the transition from SMRPG -> Paper Mario 64, most things stayed the same from 64 -> TTYD, likely as a result of same name branding and the fact that it kept the same developer this time around. At face value, TTYD is a reskin of PM64, with new areas, plot, and characters. However, if it ain't broke, don't fix it: as seen by the Metacritic link above, TTYD is the most highly rated Mario RPG, with fans singing its praises.
TTYD shines in how it refined the 64 formula: it took full advantage of its paper aesthetic, with Mario turning into paper planes, paper boats, and rolls of paper, and benefited also from the boost in hardware from the Gamecube, allowing many characters on screen at a time. TTYD also boasted incredibly creative segments where you would suddenly be placed in the control of the enemy, as in the Dooplis scenario, recreations of classic platforming in the Bowser segments, and entering pipes that led to the backdrop of each area. TTYD may have treaded extremely similar ground as the game that came before it, but its execution left it a beloved entry in the franchise.
Mario and Luigi
Developed by Alphadream, this was the portable cousin of Paper Mario. Opting for a more straightforward, yet still extremely recognizable and creative 2D sprite style, Mario and Luigi's main attraction was - you guessed it - the spotlight on the Mario Bros, rather than just Mario. The battle system was again an action oriented, timed button pressing affair, only this time it forewent the partner system to focus entirely on Mario and Luigi. Bros attacks and abilities hogged the spotlight in and out of battle, with the Mario Bros working together to spin, roll, and hammer their way across the Beanbean Kingdom.
Oh, that's right: the M&L series took us to another new land with its own race of people, the Beanish, paralleling the Toads of The Mushroom Kingdom, and brought us to locales with a unique laughter theme to their names, such as Teehee Valley or Chucklehuck Woods. Bowser once again took a role as a supporting character, leaving the spotlight to new villains from the Beanbean Kingdom. Perhaps the biggest treat for fans of SMRPG was the return of Yoko Shimomura as the series composer, lending a similar atmosphere to Mario's first RPG outing. (Sunken Ship theme remix, anyone?)
Mario and Luigi: Partners in Time
Bringing us back (quite literally) to the Mushroom Kingdom, PiT took full advantage of the DS and used its dual screens to offer refinements to Superstar Saga's gameplay. Playing off of the "dual" theme, Mario and Luigi teamed up with baby versions of themselves, with much of the game taking place in the Mushroom Kingdom's past. The alien race of Shroobs took the center role as the main enemy, harkening back to the "group villain" role the Smithy Gang played in SMRPG. PiT made some controversial changes, such as removing the overworld for a point and click world map, but it was by and large a very similar game to Superstar Saga.
Mario and Luigi: Bowser's Inside Story
This is where the M&L series really started to diverge. While it kept its turn based, timed button pressing battle system, BiS forewent the Bros moves established in the first two games and instead gave control over to the King of the Koopas, Bowser himself, for the overworld segments of the game. Bowser fought alone, but was much more powerful than Mario and Luigi combined. As a result, he fought stronger enemies. He also came equipped with his own moveset, entirely unique from either Mario Bro. Bowser also introduced giant battles to the series, creatively using the DS turned on its side for extremely unique and satisfying boss battles.
Mario and Luigi were, of course, still central players in the story and in gameplay, but their roles changed significantly: for a good portion of the game, they remained stuck inside of Bowser, and their gameplay segments played out on a strictly two dimensional plane. Bowser was definitely the star of this game, even if the two Mario Bros were present throughout; he carried the brunt of the story and was in charge of at least 90% of the game's map traversal, with Mario and Luigi only becoming able to retread his steps towards the end of the game.
Mario and Luigi: Dream Team
The first 3DS entry, and perhaps the most polarizing entry in the M&L franchise, Dream Team gives the spotlight back to Mario and Luigi. Well, actually, it mostly gives it to Luigi; the game was released in 2013, Nintendo's Year of Luigi, and gives extra attention to Mario's neglected bro. Taking on a unique dream world mechanic, Dream Team has a normal and dream version of each area of Pi'llo Island. The normal areas function much like those from the first two entries, while the dream worlds were reminiscent of the areas inside of Bowser in BiS, only this time with their own unique dream world gameplay.
While the game was incredibly progressive in the sense that each new area introduced a new ability and way to approach the game, it was also derided for its extensive tutorials, which were perhaps a side effect of attempting to cram so much newness into every area. Overall, Dream Team has the most advanced presentation in the M&L series, with gorgeous spritework and a fantastic OST, and is an incredibly innovative entry not only in the RPG spinoff series, but in the Mario franchise as a whole. Its experimental nature leaves it rife with flaws, however, leaving it as highly praised by some as it is lambasted by others.
And then we have the two black sheep.
Super Paper Mario
Released for the Wii as a pseudo-sequel to The Thousand Year Door, Super Paper Mario abandons its RPG heritage for a strong focus on platforming. The text heavy plot, an emphasis on characterization, a quirky setting, and the existence of hit points are all carried over from Paper Mario proper, but gone are the turn based battle system and 3D field maps, replaced with the traditional 2D planes that classic Mario games are known for. While not an RPG in the traditional sense, SPM still features an intricate, chapter based plot, and is also the only instance in the series where Luigi becomes a playable character.
Paper Mario: Sticker Star
Deviating from the series' position as the "console" branch of the Mario RPG series, Intelligent Systems released Sticker Star for the 3DS. Sticker Star heavily relies on stickers as a gameplay mechanic, with each sticker resembling a real world object, such as a pair of scissors. Apparently a victim of a development crisis, Miyamoto himself signficantly turned the tables on the game during the time it was being made. IS was given orders to remove "non-Mario" characters and to make them instantly recognizable faces from the franchise, as well as to de-emphasize the text heavy focus that the series was known for, opting for a game with little to no dialogue, plot, or character interaction. Needless to say, this upset quite a few fans. Nonetheless, many praise the game for its stellar soundtrack and captivating world design.
Mario and Luigi: Paper Jam
The next entry in the series attempts to combine the Mario and Luigi series with the Paper Mario series, although it seems to be first and foremost a M&L game. The game was recently released in Europe, and will be making its way to the states in January. I think it looks like it has more promise than Dream Team, and certainly more than Sticker Star, although I am a bit concerned about Paper Mario playing second fiddle. Time will tell where it ranks among the rest.
As for my personal favorite, it has to be the original: Super Mario RPG.
I loved this game. I love this game. This game is amazing and anyone who likes Mario and/or Final Fantasy should play it. I've replayed this game probably over ten times in my life and I just did it again recently. Why do I love it so much? Nostalgia, mostly, since the game hasn't aged particularly well, what with its dated 90's RPG mechanics.
But at the time? It was a powerhouse, not only because it's a fine RPG in its own right, but because it was the first to take Mario and put him in a game with a real narrative. I don't think anybody could have seen this game coming, especially because the king of RPGs, Squaresoft, is the one who made it. But it's not all nostalgia. There's a few reasons I keep coming back to this game in particular.
-Yoko Shimomura is at her finest here. Every track represents the cheerfulness and whimsy of Mario fused together with the fantastical, grand scope of an RPG.
Beware the Forest's Mushrooms
The Road is Full of Dangers
Grandpa and the Delightful Tadpoles
Where am I Going?
Fight Against Smithy
-The game oozes charm and atmosphere.
-The timed attacks aren't innovative by today's standards, but back then they were a pretty big thing, and they're still fun to use. Timing spells is still kind of awkward, but it's extremely satisfying to time something right in this game. That extra clunk from Mario's shells, the extra hit from his hammer, Bowser's spike chain remaining in the enemy and protruding its spikes to hit them again and again... you feel like your extra input has done something. I think the sound effects really make it work.
-Beginning the game with a fight against Bowser, only to have him usurped by a greater evil, is great. The Mario and Luigi RPGs play off similar concepts, but never to the extent seen here. Bowser later becomes a full fledged party member in order to take back what Smithy and his gang stole. Bowser's Inside Story played off the playable Bowser concept, but never again has he actually stood side by side with Mario until the very end of the game.
-Smithy's gang has such a presence throughout the game. From the time you're ousted from Bowser's Keep, to the dark and ominous arrow-infested Rose Town, to the strange goings-on in the Moleville Mines, all the way up until the end of the game, you feel Smithy's presence in the world. Bowser seems like a one-note villain compared to him. The Final Fantasy esque "journey to save the world" trope really bleeds into the way this game is set up, and seeing something like that in the Marioverse is so awesome.
-Geno is in this game. The world is so at risk that a being from a higher plane comes down to assist Mario. I absolutely loved his story as a kid, although nowadays I often think they could have explored it more in depth.
-The art style is great. I love the spritework, and, like the game does with its music, the settings are usually creative and a nice blend between fantasy tropes and the weirdness of the Mario world.
I want a real Super Mario RPG 2. Until that happens, though, this game will always be up there as one of the best.