looking for a new FPS game

I've looked at all the reviews and game vids but i'm still confused about what to get there are too many good ones out now. I am getting a new comp and want to get into gameing again, the last FPS game i got for the PC was UT2004.There a a few things i'm looking for when i'm getting a FPS.

1. gameplay, I don't want the controls to be to complicated. also I don't mind about graphics, if the gameplay is awsome i'll forgive that part.

2. Multiplayer, has to have a good strong community with some staying power, hate when I buy a game and there is no one to play with.

3. single player is fun, I'd like to play offline but not as important to me as multiplayer.

What are the best options if i was to say i'm just going to get one maybe two games (there are so many but i don't want to splurge to bad.)?

Edit: I forgot to ad i'm looking at PC games only

"Combat Arms" by Nexon is a good multiplayer FPS game. It is pure multiplayer though, but the bi-monthly update makes up for it. But, the best part is... its FREE! They use this macro-transaction system so you technically don't need money to get full access of the game.

Halo 3, if you don't have it already, is also fun. Good graphics and gameplay, plus the great multiplayer community.

Orange Box for sure, then Call of Duty 4.

Now I don't know if you're one of the CoD haters, but this one has an extremely fun SP and a MP that lasted me 50+ hours and I don't even play MP games :)

get them now!