I prefer single player games to multiplayer, but I will (rarely) play multiplayer against other people, depending on the game and the people. I don't like online multiplayer much, as I mostly don't know the people I'm up against, and so (a) it's not nearly as enjoyable as playing against your friends, and (b) the most enjoyable multiplayer games I've ever played (Goldeneye/Perfect Dark/Halo/Timesplitters 2 and 3, etc) have been split screen, as by far the best multiplayer gaming experience is when you're in the same room as your mates, so you can laugh at them when you're winning and insult then when you're losing. It's a fantastic experience, unlike the mostly clinical experiences I've had when playing online.
Then there's the other extreme, when multiplayer online is far from cold and clinical, which is when you get racist/immature/brave-because-they-are-anonymous-and-behind-a-monitor-screen morons who hurl abuse at you, or quit if they are losing, or think it's somehow funny to shoot/hinder their own team mates.
Or, in a way this is worst of all, when the only people you can find to play against online are extremely skilled and you just get killed repeatedly before you even get a shot lined up yourselves. This latter situation is all you get with many online games when it's been out for a while, and most people have abandoned it for the latest Medal of Duty XXXVII, and the only players left have been hammering it for eight hours a day, seven days a week since release, and know everything about the game, and the learning curve you, as a newcomer, face is all but insurmountable.
What I do really like is multiplayer where their are good bots (computer controlled opponents), as you can play against these at any time (even years later, when you're the one person on planet Earth who is still playing the game), you can play on the maps you like, with the settings you like, the bots don't rage-quit/shout abuse/deliberately kill their team-mates/etc, and it helps you get to know the game and get better at it (by facing higher skilled bots when you choose) in case you do want to play other humans online.
And if the bots are good enough then playing against them can be really enjoyable. My favourite multiplayer-against-bots games are Perfect Dark, the original Unreal Tournament (1999), Unreal Tournament 2004, Unreal Championship 2, and Timesplitters 2 and 3). I don't like class-based/streak-kill/etc type games, I much prefer the everyone's equal old-school death-match type games. I've put countless hours into these games with just me and the bots, and though it's not nearly as good as playing against your mates, it's still enormously fun. These are games I honestly don't think I'll ever abandon, as I can pick up and play them any time and it just feels right.