Well I've gotta keep my Photoshop abilities rust-free right? Here's Halo: Reach mashed with Call of Duty 4's game cover, just made for the sake of it really. Surprisingly difficult getting everything to look so similar to the original that I didn't notice when I started, there's no greys - it's all tones of green, added noise on top, (some of) the particles flying at the feet and the lighting were just some of the many tiny things I had to edit to match the original CoD4 cover.
Looks pretty accurate, IMO.
[I am not trying to get across a point about Halo or Call of Duty, I just thought it'd be cool to make this.]