I'll add a poll if there are enough replies.
Mine:
Top 5 Most Loved:
1. Super Mario World - SNES
2. Super Mario Bros. 3 - SNES version on All-Stars
3. Super Mario Bros. - NES or SNES (either version rocks)
4. Yoshi's Island (SMW2) - SNES
5. Super Mario 64 - N64
(I love my SNES

For the sake of it, here are my most unloved:
1. Mario's Time Machine - SNES (epic fail)
2. Mario's Missing - SNES/PC/NES (you played as luigi anyway)