FRAK!!
Oh MAN the memories. :) Seriously, I wasn't sure what was so great about this game.
Mario 3 had four way interaction, you could interact with enemies in different ways, multiple ways to finish a level, there's never been a game like it IMO.
Prince of Persia got me hooked, though I never did get past level 11 without the Levset+<CTRL+L> cheat. It was just so smooth and had a wide range of animation frames- It was just a fantastic game for it's time.
Oh and LOST VIKINGS! Excelent 2D platform puzzler, I loved it. Wish I had a copy now :-) Three funny looking characters, wierd little interactions, extremely strange levels. *sigh* I wish there was a new one :-)