1. Legend of Zelda - what games should be
2. Mario - doesn't need explanation
3. Metroid - Metroid Prime is the first FPS I didn't get sick of after 10 minutes
4. Mario sports (tennis, golf, kart, baseball, etc.) - they can make *ANY* sport 10 times more fun
5. Metal Gear Solid/Splinter Cell - they're too close to choose but I love the stealth action
Guitar Hero can have an honorable mention cuz it's still a relatively new franchise and with GH3 it's really gonna pick up some steam.