Im also a fan of Mario Bros. Games. I loved all the Mario series, from Super Mario Bros 3 to Super Mario Sunshine (except the very first one Mario game, the one that came with Duck Hunt )
There are also many Nintendo games of Mario that are pretty good, but are not counted as the original mario series, like Haieto said, for example Paper Mario (a great RPG, a game packed of content) Super Smash Bros Melee (my alltime favourite console game ) and Mario Kart.

I think this is one of the most difficult decisions I would ever have to make. I would say that it would be a tie between super mario bros 2, super mario bros 3, super mario world and super mario 64. Then I thought, ok, lets say I have all 4 games right now, which one would I want to play first, and my decision was super mario bros 3, I guess its because I remember it being really really fun and I havent played it nearly as much as super mario world or super mario 64. Then on second place it would be super mario 64, I guess because you have a lot of freedom to play almost any map in the beginning, and then it would be either super mario bros 2 or super mario world, I think I picked super mario bros 2 before super mario world because I havent played it in a while either.

I have yet to play the new super mario galaxy game, it seemed fun, but has anyone noticed that the super mario games arent as creative as they used to be like say from super mario world and before? I remember the graphics and all were really crazy and creative, lately the games try to imitate what is real to much.. at least thats how I feel about it.

I just loved Super Mario World.. The was the happiest guy in the world at the time when i finished Super Special level, and when the whole game changed! Absolutely Awesome and Unexpected at that time!
Super game, one of the best games ever created, after pong, and pacman

my favorite mario game is mario 64 and mario kart those where the games that keeps you up until 12 even thou there was no online it was still fun but now there are people who beat the whole game in 10min i think it is less but i forget the record now there is xbox live and online and mario has been under my bed catching dust with my nintendo 64.

I really liked the one who comes with the nitendo 64 but my favorite remains the old ones like super mario bros 3.after all those year I still love play that game lol.

Gotta go with New Super Mario Bros for DS... Super Mario world was my favorite before this one.

I don't play handheld systems, so I'm not familiar with any of those Mario titles.

Super Mario Bros. 3 (NES) was probably the best as far as games that I can actually play goes. (N64 and every console after that...ehh, I get nauseous and dizzy when I play those systems). Mario 3 was cool because the graphics were pretty good for the time...Mario could actually fly...etc.

I actually like the first Mario Bros. game more than I like 2. Mario Bros. 2 is such a huge departure from the overall concept of the games. I mean...having to catch eggs and throw them back at the dinosaurs or whatever at the end? Not really my thing.

I have to say, SM64 is definitely the best. It really defined 3D platformers, and none other have ever reached it's greatness.

I would have to say Super Mario Bro's 3 was my favorite along with Super Mario Kart and world for the snes are favorites because of the replay value they had back in the day I play them from time to time on a emulator. We use to spend hours racing each other in mario kart is was some good fun back in the day.