I strongly advise anyone to get altitude. Its a 2d multiplayer plane game. Its got a 3 hour free demo too
http://store.steampowered.com/app/41300/
If its anything to go by I've played 578 hours.
I've played WoW, Bioshock, Mass Effect, Oblivion, Eve Online, Dragon Age, etc but this has the most replayability and longest life of a gave I've ever seen. Even a ton of teamliquid starcraft people play it. I strongly advise giving it a go.