This is the best tower defense game I have ever played. The art style plays a big role in that, though. But it really is top notch. A new game with retro vibes.

Simply put, TF2 has become the best shooter of all time. It has proven its staying power for years now: the timeless art style, the classic gameplay, the support from one of the best developers. The mirco transaction based free to play model is a sign of things to come, as TF2 is the herald of a new age in computer gaming.

If you're looking for an online shooter, this is the one to get. It's more of a pc shooter (tweak friendly) than MW2 was. Though it has it's technical flaws, I'm sure they'll get fixed as Treyarch is supporting the game post launch.
The class system with the perks and weapons make for a ton of strategies and if you're a completionist, you'll come back time and time again, be it to unlock the next weaopn, or the next prestige.