My top 5 games are:
1 - Super Mario Advance 3 (Yoshis Island) - trying to get 100% on every level still has me gripped to this game.
2 - Zelda II (The adventure of Link) - my first experience of Zelda.
3 - Super Mario World - still fantastic to play after all these years.
4 - Resident Evil 4 - This games is very satisfying - maybe its the shotguns shots to the head which explain it.
5 - Metroid Prime - a gripping adventure & truely unique.