FF:III on the S-NES is probably in my top 5 games of all time. But I don't think I've ever actually beaten the game, because I can't stand Kefka's tower at the end! You have to control 2 (3?) different teams walking through, hitting switches and stuff for each other. My desire to not use a walkthrough meant I got into about a million mob-fights while I was wandering around.
The other game I haven't seen mentioned yet at all is Lion King for the Sega Genesis. Good god! The entire game, after the 3rd level, is a wall!