im srry i must disagree. Apart from Gmod of course cod mw2 had the best multiplayer experience ever. The leveling up was cool, the weapon customization, the tags and emblems, the challenges. Its SUPA fun. I have never played Battlefield but CoD to me is one of the best games ever. Don't rage at me for my opinion, please.
TF2 > CoD.
Why?
I will list reasons.
1. TF2 has very unique characters, each with his own personality, background, nationality, and life story.
2. Weapons are balanced.
3. Frequent and FREE updates which include brand new COMMUNITY made maps, weapons, and hats.
4. Customizable inventory which includes paintable hats and nameable hats/weapons.
5. An in-game trading system which has developed its own mini economy.
6. Fun, even after years.
7. A unique art style which is funny, and not serious. - Basically what a game should be.
8. A whole story behind the game and it's characters, which is available in the official TF2 blog.