I can't answer All-Stars because that is a total cop out. World is the true answer. It has the best music, the best secrets, and the cape is functionally the best power up.
3 is second since it is definitely a fantastic game just not as good as World in most cases. Plus it has the coolest power ups.
3D Land is my third. I feel like it is easily the best 3D Mario game but I missed the Galaxy games so I could be wrong on this one.
Super Mario Bros 3 was my first game ever, but Super Mario World is likely my favorite in the series. I've always enjoyed the fans' rivalry between those two.
Also, I agree that it's pretty silly to include Super Mario All-Stars + Super Mario World on the list. That's easily the obvious answer.
Putting All Stars on the list kind of breaks the poll. It's not a game; it's a collection of games, and gives people who enjoyed all the NES games (and World) an easy out without actually making a decision.
I really enjoy 3, World, and Yoshi's Island about the same, making it really difficult to choose. Mario Bros. 3 was the first game I ever personally owned; before that anything I played was at a friend's house. Yoshi's Island was just an amazing game and a very interesting diversion from the typical Mario gameplay, while still feeling like a Mario game at its core. But I probably put the most time into World out of the three, just due to it being the only SNES game I had for a long time (not to mention all the secret stuff to discover), so I guess I'll have to use that as the tie breaker.
I would say either Super Mario Word or Super Mario Bros. 3. I had Super Mario Bros. 3 for the NES, and then I got the All-Stars pack in with my SNES that had everything on it.
I have the fondest memories of Super Mario World, but Super Mario Bros. 3 was literally the first video game I've ever played so it has a special place in my heart.
I wanted the poll to be exclusively about the mainline Mario Bros. series of 2D scrolling platformers, and not just games starring the brothers. So games like teaches typing are out, as well as Paper Mario, Dream Team, vs. DK, etc. I left one option for people who only like the 3D non-linear games (64, Galaxy, Sunshine). I consider 3D Land to really be a 2D game with polygonal graphics, like some recent Sonic games have been... it's really just a spiritual successor to game boy Mario Land, and plays so. I also left an option for non-Mario Bros. platformers built on the same gameplay engines like the original Doney Kong or Super Princess Peach, or sequels like Wario Land 2-4. Finally, I included All-Stars cause its basically significantly changed versions of the first three games running on the world engine and sound scheme. I've always loved those remixes best.
@hunter5024: Yeah, I beat 3D Land long ago. But I'm always getting back into it, because I'm always impressed at how smoothly it incorporated 3D into its levels. The level design in that game is fantastic.
In the second half of the game especially. The things they do with shadow mario and time are impressively smart.
World, come on. Either Super Mario Bros 3 or Super Mario 3D Land is the second best and neither even come close.
Also props for including Super Mario Bros Special even though nobody would ever pick it due to a combined factor of being obscure and kind of shit.
Edit: Didn't notice the All-Stars + World option, that seems like a complete cop-out since it's just a compilation of the best Mario, the game a lot of people mistakenly call the best Mario, and a few other solid Mario games.
Super Mario All-Stars & Super Mario World is the superior product because it contains SMB 3+World and the originals, with improved graphics.
However I still vote SMB 3 because I'm, as they say, an idiot. I don't know. I'm just overly biased towards SMB 3 and didn't really like what they did when they improved it graphically for the SNES, and I'm just not that into World.