This is just a fantastic article about why Gen Y is unhappy (despite the not-obviously-great title): Why Generation Y Yuppies Are Unhappy
The TL;DR is just that we (I think it's we, I might be on the border between X and Y), for our entire lives, have set our expectations high and, by definition, not everyone can be exceptional. Or, basically, this awesome equation:
The only bad part about the article is that there's effectively no way to break the cycle without a) a massive depression of expectations (in this generation or the next) or b) millions of people working to hard to be happy with what they've got. I don't see either happening any time soon.