Super Mario 64 is my favorite of all, though that gets nostalgic benefits that help it out since compared to the newer games it's a lot less refined in many ways. The actual best looking/feeling/playing games would be Super Mario 3D Land or Super Mario Galaxy 1 for me. Why I'm personally EXTREMELY excited for Super Mario 3D World!
Upcoming Games To Get
Definite: Kirby Star Allies (Switch), Mario Tennis Aces (Switch), Fire Emblem (Switch), Yoshi (Switch), Pokemon (Switch), Kingdom Hearts 3 (PS4), Monster Hunter World (PS4)
Considering: Fe (Switch), Donkey Kong Country Tropical Freeze (Switch), The World Ends With You (Switch), Ys VIII (Switch), Street Fighter V: Arcade Edition (PS4), Kingdom Hearts 2.8 Remix (PS4), The Last Guardian (PS4), Shadow of the Colossus HD (PS4), Anthem (PS4), Shenmue 3 (PS4), WiLD (PS4)