Games I've played for 6 or more hours straight [probably half of them but still a shitload].
Sonic 1, 2, 3, Spinball
Sonic Adventure 1 & 2
Quake
Serious Sam
NiGHTS
Drakengard
GTA 3, 4, 5
Mario 3
Mario 64
Pokemon Red, Blue, Yellow
Mario RPG
Paper Mario
some Tomb Raider game for Dreamcast
Unreal Tournament
Castlevania [forgot which number]
Zelda 3
Zelda Oracle of Ages/Seasons
Zelda:Ocerina [sp?] of time
the list goes on...