Having played a good bit of GTA's Multiplayer, both DM and TDM, I reckon that a DM with only around 3 or 4 people, over an open area is definitely the funnest way to play, games with tons of people are simply too fast and chaotic.

Also, auto-aim sucks big time.

Auto-aim ftl. Where's the fun in a guaranteed death everytime you drive up to someone in a car?

My best experience with GTA multiplayer was when I versed I guy in a car vs car duke out. We both had an infernus each (don't ask me how they spawned...) He had a sub and I had pistol, so my tactic was to try and run rings around the guy, trying shoot him up as much as possible. I won. With Auto aim, I find that if you have an AK or M4 you can simply auto aim at someone miles away and it's all over, there isn't an tactics, it's just mash aim/shoot until you die. My problem is that spawn distance is always to close, you spawn, you run for 10 secs and then killed by a guy way across the parking lot you can barely see. No tactics, no fun.