Halo 2 > Halo 3 > Halo 3 ODST > Halo Reach > Halo CE
Based on campaigns.
Imagine a game thats a cross between mario 64 and halo. It would be Master Chief running around courses and collecting stuff. The bowser battles would be battles with a prophet, trying to save the universe from halo. Goombas would be grunts. Levels would be revamped to look forerunner or something
Sounds pretty good right?