Hey, I've always wanted to get BC2 PS3 edition but for one reason or another I always ended up buying other games, I want to know what is the state of the multiplayer right now because if it's already dead I won't invest that money on BC2 Ultimate Edition just to pay more to only play Vietnam, I want to play Vanilla BC2, Vietnam and BF 1943, should I get the game? (PS3 Edition)

Not sure about the PS3 but when checking bfbcs.com it says that  19 263 are currently online on the PS3 and that's of the ones that have registered their characters into the database.

people still play but not as much as there used to be.

You can still find full servers of BFBC1 on the 360 today. There will never be a lack of players.
 
Also, people who have Vietnam don't only play Vietnam. They still like the regular game just the same.

It's extremely buggy, I would dissuade you from buying any version of BFBC2.

There are actually more players on vanilla then vietnam. 

You should have no trouble finding games on the PS3. Both vanilla and Vietnam.

PS3 alive and kickin', despite all the problems it had the past month or so. Everything's up and running again and it's pretty much on 24/7.