I'm not that much into massive online gameplay. I like myself some Singleplayer action and as funny as it may sound: I actually like XBL better than the PSN even when I play on my own or with just friends.
Playing online feels quite awkaward to me as people who usually play a game online love it and are pros. Well, I play occasionally and for fun and as such I don't really enjoy being murdered over and over again.
(Mind, I'm not crap at video games, but getting stuck in lv 900000 prestige player matches in MW2 is quite annoying, even when I'm usually not at the bottom of the foodchain
It's not that I don't like playing with others, it's just that I love playing splitscreen with "physical" friends - it's probably got something to with how I was raised on (and still love) classic video games.
Probably because of that, my favourite feature is the ability to
log in two XBL accounts simultaneously for split-screen co-op. People usually take this for granted - those people never played on the PS3. I love me some Rock Band 2 - and I play it on my PS3 - my guests are always annoyed that they cannot log in with their PSN accounts.
To be honest, it's a shame that gamers these days tend to limit their interaction with other players. I thing that games are more fun when shared with others: when you can laugh in their face when they lose, or annoy them just to get a couple extra points. You say you interact over Live? No, you talk to a box and if you are lucky you don't get to listen to a nazi 12-year old.
And if that doesn't count, because that's kind of a anti-live feature (we do play online though, even when we play split-screen!), I really appreciate the (mostly forgotem)
TrueSkill/Rep system. Yes, I know it's flawed and yes, I think the big M should put more time into it but I use it a lot to actually see if a person (be it a friend or a stranger) is worth dealing with. (TrueSkill on Magic The Gathering acutally helped me find a couple friends on similar skill level - playing with those people made the game so much better and intense) That's one thing I would love to see implemented on the PS3 in the future, btw.
There, and sorry about the wall of text