Wouldn't it be nice if you could access the Apple App Store, download a free game and play it on the big screen?
Have an iPhone or iPad? Play all your games mirrored to the TV through AirPlay. I've played Angry Birds plenty of times on my 50" plasma. Looks great too!

With an Apple TV you're pretty much limited to what you can "buy" in iTunes.
I have ripped my entire DVD/BluRay library into iTunes complete with tags and cover art. All of these are available to my Apple TV.