Counter-Strike and DoD:Source are the ones I've had the most fun with =D

CS

Terrawars.

"Call of Duty 4
Team Fortress 2
"

Team Fortress Classic

Battlefield 2

Halo 1, 2, and 3

Goldeneye is worth a mention as well.

On PC I'd say Tribes.

Counter-Strike.  There is no denying it.

I think Left 4 Dead will be up there as well.

I think Left 4 Dead will be up there as well.

man this is a tough one and ever since i saw this thread i've been thinking about it long and hard and still cant really descide on which games i personally think has been the best multiplayer shooter..... Because of the hour's that i spent on this game, and had such a huge Clan base, maybe even one of the first FPS games to have clans, would be Delta Force 1 (the original) back in the 90s... I spent litterly months and months on the novalogic servers and the clan based servers.... I believe it was even my first multiplayer experience really outside of doom on lan.... i used to get really freakin pissed at the lag you would get on that game (dial up so sucked ass) even when all we had was dial up lol....
The original Unreal Tournament would be a close 2nd because at the time it revolutionized how multiplayer FPS should be played, modded, and brought communities of gamers together all under one game.... it was original and one of a kind.....

Not much to say really but thought i'd at least mention those in here..... Alien vs Predator used to be hilarious!!! online, ppl would always use the predator disc in the hallways and if you timed it right, just used to jump right over them and totally kill everyone with the minigun lol.... but that game's best experience was singleplayer to me..... series sam 2 was fun as co-op and lets all not forget the Battlefield series.......

But yea at the end of the day, Delta Force 1 was my personal fav shooter to play online with UT a close 2nd

Tribes (1 or 2)

Counter-Strike 1.5/1.6/Source

I wasn't there for the beta days, but I still play CS even today.

"The one I've played the most would probably be RTCW and RTCW:ET, followed by Quake III and CoD,UO,2,4.

I'm going to go with the Free Multiplayer game only, RTCW:ET.


"

I think CoD4 is the best, but I like TF2 and Battlefield 2 a lot as well

Call of Duty 2 is my all time favorite.

css for pc.
halo 3 for 360

Doom 2 and Quake is all I need.
Quake 3 is quite perfect also.

Counter Strike : source

UT2004

I would agree with the COD series.  More specifically COD 2 and 4.

All time has to be Counter-Strike 1.6.

Counterstrike Source

Battlefield:bad company.

Quake 2

I like BF2

Counter strike started it all with the military theme to my knowledge at least so I  have to say that since most multiplayer games at the time were twitch base. Battlefield series for the vehicle, infantry, battles with many other players gets second place. More recently Team Fortress 2 but only gets third place because I am more into military shooters.

If anyone makes a thread called "best multiplayer shooter of all time" and doesn't put the words "Counter" and "Strike" in the thread, that person is stupid.

I can't believe how many of you are talking about Call of Duty. If you're going with Call of Duty, you may as well just say Quake 3. The CoD series, while fun, doesn't pretend to approach the skill and nuance of Counter-Strike. CoD gets boring for old school CS players because it's not fun to win something so easily, the reward of this kind of game is in overcoming a challenge and succeeding as an individual and as a team. When I play CoD4 I'll consistently outplay everyone, I've had the pleasure of mocking entire teams of clan players at being beaten by a single pubber. CoD is barely one step removed from deathmatch, it uses a Quake derived engine and always felt a bit too much like it to me.

I hope I'm not the only person to say Perfect Dark.

CSS

Wolfenstein: Enemy Territory takes the cake. It had lots of great classes, unique objectives, a variety of great maps, and was more fun then any other multiplayer shooter ever. Oh, and it was completely free.

Counter Strike and CoD4. CS was a lot better, though, in my opinion...No helicopters or air strikes, just real, first-person fighting.

quake 3, it is pretty much the basis for what a shooter should have.

CS. Oooh yeah.

I don't know about best, but I would handily consider Counter-Strike as the most important.  Followed by the Quake and Doom games in a dead heat.  No pun intended, there.

one of my favrioutes are quake 3 arena

ok, CCS, TF2, Cod4, Unreal Tornament, Quake 3, Battlefeild 2

Quake 3

Quake 3 Arena! Woohoo!

for me it is a tie between Unreal Tournament and then Battlefield 1942

"Wolfenstein: Enemy Territory takes the cake. It had lots of great classes, unique objectives, a variety of great maps, and was more fun then any other multiplayer shooter ever. Oh, and it was completely free."