I pressed other and it's really a combination of all of the above. although I especially hate it when people want to win no matter what, as opposed to trying to test their skill face to face. sure, in a real life combat situation im sure many people would choose tactics to ensure a win at the expense of their fun.
As an example, I was playing GTA4 online yesterday and having great fun in freeroam with a couple of friends making up our own game modes and things. we then thought that we would swap to cops and crooks and we were surprised to find a fair amount of people in the lobby (surprising for a game that's been out for over 3 years).
Now, for those who don't know, this is a game mode where the crooks have to escape to a specific getaway vehicle (either helicopter or boat) marked on their map, and the cops have to try and stop them getting to the getaway vehicle without actually knowing where it is.
The getaway vehicle location is randomised, but there are only a few possible places it can spawn which is relatively easy to work out by noting where the crooks spawn and what direction they start heading in.
What most people do as cops is head straight for the RPG, assault rifle and helicopter and fly to each possible location until they find the getaway vehicle at which point they'll either a) camp out and kill anyone who comes to the getaway vehicle. b) park the getaway vehicle somewhere inaccessible and then camp or c) destroy the getaway vehicle on sight.
and as crooks all they do is swim to the middle of the ocean out of range or head for a helicopter.
As well as this, any sort of team based objective game your average team mate is completely hopeless. Now not hopeless as in a lack of skill, but hopeless in a lack of teamwork. I can't count the amount of times that I have carried the enemies flag across the entire map at a painstakingly slow pace whilst my team mates whiz past in the opposite direction in vehicles with passenger seats. A few times I've been killed at the last hurdle just outside our base and yet still no one thinks to pick up the flag and walk the last few feet.