2. Super Mario Bros. 3 (NES)
There's been quite a few Mario games in my list, be they 2D platformers, 3D platformers, Kart Racers or whatever else, but it's Super Mario Bros. 3 which takes pride of place as my favourite Mario game ever made. We poor souls in the West didn't get the true SMB2 at release, instead we were given Doki Doki Panic, so when SMB3 came around, it was a welcome return to the format of the first SMB game. It came with multiple new power-ups, most notably (and most memorably) in the form of the Super Leaf, the Tanooki Suit, and the Frog Suit. These new power-ups greatly added to the gameplay, and thus made it far superior to what had come prior, and made it the foundation for everything that was to come later, and that's why I rank it as the best Mario game.
I'm not giving any clues for number 1.