I’m working on collecting screenshots for 4 (yeah your read that right, 4) game reviews. Halo, Call of Duty, Halo 2 and Call of Duty 4: Modern Warfare. Actually, I need to complete the last 2 games before I can write a review 
Let me just give your a brief review about each.
Halo is addictive. Graphics are nice. Sound is crisp. Gameplay is awesome. I finished it on Legendary. Muhahahaha…..
Call of Duty is serious. It’s real. Very good AI. Nice guns, even though they’re WWII, and I love chucking grenades inside bunkers. Finished it in Veteran. Nice game.
Halo 2. It retains the fun gameplay of Halo the original, with a improvements in textures, sound, and not to forget, Physics. Awesome effects now. Grenades do chuck things around you!!
Call of Duty 4 is almost about to kill my PC. Although it loads much faster than Halo 2(!), it requires some serious number crunching for the full effects, but the game is very scalable, unlike Halo 2.
Coming up first, Halo.