Korppi on 21 February 2012
Only including games that I've completed 5+ times:
Super Mario Bros. 3 - 5 times
Ratchet & Clank 2: Going Commando - 5 times
Sonic & Knuckles - 5 times
Metal Slug 2/X - 6 times
Lylat Wars - 8 times (Not because I particularly like it, but because it's short as fuck, and has multiple branching paths)
Warcraft III - 12 times
Super Metroid - 15, at least. (Only four or five of them were 100% runs, though)
