I don't have the attention span for single-player games anymore, and prefer gaming as a social activity. Though multiplayer is better when playing with people you are familiar with.
Also is it just me, or was Xbox Live better, and more social, back on the original Xbox? Unless their microphone broke, everybody on Xbox Live had a headset, and sometimes the host of a game would go as far as kicking people without one because the norm at the time was that everyone was using voice chat, and actually talking. Two of my favorite games on there, Midtown Madness 3 and Steel Battalion: Line of Contact, I would have not enjoyed nearly as much, nor played for as long as I did, without everyone utilizing voice chat. They also had some pretty decent communities on those games and the voice chat resulted in some of the best teamwork I have ever seen in any online game to date.
On the Xbox 360 at this point, you rarely see people with a mic plugged in, or they are in a party chat with their friends so you can't communicate with them anyways. On Halo 4 for instance, even when playing team-based modes, no one is communicating or actually working as a team.