Super Mario Bros. changed my life forever, and then SMB3 changed it again. Pretty much all of the Mario games are excellent and groundbreaking in their own way.

SMB3 is my favorite, though Yohsi's Island is pretty much as close to perfection as you could get for a platformer.

Where would 2D platforming be with out SMB or later SMB3?
Where would 3D platforming be with Super Mario 64? Man, that was a great game.

The Galaxy games were great too, they were a better follow up to SM64 than Mario Sunshine. So far the Wii U is lacking that groundbreaking Mario title to make it worth owning. New Super Mario Bros. Wii U looks ok but nothing new. The original New Super Mario Bros. for DS was great though and it was a very wise decision by Nintendo to take the Mario series back to its 2D roots. It paid off big for them.