Halo 1 Halo 2 Halo 3 Halo ODST Halo Reach For its simplicity with weapons but also the amount of balance and glitches it can give you, making a huge laugh sometimes (check out "Halo 3 Top Ten *********" and there is a series of about 60 videos, they are all very good !)
Battlefield 1942 Battlefield Road to Rome Battlefield Vietnam Battlefield 2142 Battlefield 2 Battlefield 2 Special Forces Battlefield Bad Company Battlefield Bad Company 2 Battlefield Bad Company 2 Vietnam Battlefield Heroes For the interesting gameplay which all other games have not yet approached, as classes have significant difference and it much better defines your playstyle.
Call of Duty 4 ProMod only.
Age of Empires I Age of Empires I Rise of Rome Age of Empires II Age of Empires II The Conquerors Age of Empires III Age of Empires III The Warchiefs Age of Empires III The Asian Dynasties Age of Empires Online Age of Mythology Age of Mythology The Titans For the information of real life (mostly history) it could give you aswell as the map making / gaming experiances.
Mass Effect I Mass Effect II For the interesting RPG approach that also goes well with cinematics / movie style.
God of War I God of War II God of War III Dantes Inferno For the more complex fighting system (with the button coordination).
World of Warcraft World of Warcraft The Burning Crusake World of Warcraft Wrath of the Lich King World of Warcraft Cataclysm For very interesting Lore.
Those are the ones that come to mind, by the way if I missed a Battlefield Game please, please, please add it to my list !
Dragon Quest 8: Journey of the Cursed King That game destroys all competition in my mind. I could just pick Modern Warfare 2 like everyone else, but the fact of the matter it;s terrible. So what if I play it every day? It doesn't stop it being a disgustingly broken game that hasn't been fun since a week after release date.