Halo 2 > Halo 3 > Halo 3 ODST > Halo Reach > Halo CE
Based on campaigns.
Halo 2. Best story, most fun, best levels
Halo 2 > Halo 3 > ODST > Reach > CE > Black OPS > MW2 > Viva Piñata > Super Mario Galaxy > Super Mario RPG > Nyan Cat Adventure > Pac Man > Halo Wars