I picked Halo, Megaman, and Guitar Hero
HALO
Probably most popular 1st person shooter ever (other than GoldenEye 64)
It's awesome. Everyone knows what it is and it outsold everything.
And it's fun and we all pwn in our own way.
MEGAMAN
Famous, fun, and maybe the longest video game series.
From memory it has 10 retros, 9 X's, 4 Zero's, 2 ZX's, 12 Battle Networks, and 5 Starforces. Adding up to 42 games, maybe more counting foreign games and fan games. Also one of my personal favorites.
GUITAR HERO
First of it's class. People say RockBand's better, but they stole ideas from GH, so RB's the cheater.
It's what got me into playing guitar in the first place