To be a social reject or not? The decision really is up to the gamer. Personally, I'm a hardcore FPS addict who likes to spend some time with other types of games as well. I refuse to play WoW as that would just be degrading, the same reason I don't, nor do I ever intend to get, and Xbox.
The trick is to have a social life in addition to being a gamer. Go to school, or have a job where you talk with many people. Or, you could sit at mom's house, in the basement, surrounded by "Flamin' hot Cheetos" bags and empty mountain dew cans while bragging about your level 12 goblin-slapper.
Either way, I think the choice is completely that of the individual gamer. I don't think that time consuming games creates social rejects, but it gives said rejects an excuse to not talk with real people in person. Unfortunately talking with people on-line is no where near as fulfilling as a pizza at work with a bunch of friends.
The real problem is the people who encourage the complete cutting-off of real social connections in lieu of these online "conversations" being regarded as socializing. Saying "Well at least fat pizza-face Herbert has lots of little friends in his online game." is unacceptable. Especially by authority figures like parents who should be encouraging said "kid" to get a job/go to school/get a life.