I'm comfortable judging Barnes as a college player and ignoring his NBA future, for now. And his college career is, by any realistic definition, a disappointment when judged against both his media hype and his self-hype. He was, in his time at Chapel Hill, a good small forward. For parts of games he was dominant, but rarely for a whole game or for a stretch of games. He was never close to being the best player on his own team. In fact for the bulk of his career, he was the fourth best player on his team (although that is fourth behind three very, very good players in Zeller, Henson, and Marshall).
For a kid who came to Chapel Hill touted as a preseason NPOY/All-American (not his fault, that was media hype), and who talked about leaving his legacy there (that's all on him), he leaves UNC as a borderline first team All-ACC player, and his legacy is a couple of good, but not spectacular seasons both for himself and his team.
He may go on to become a stellar NBA player, but that will not change his "legacy" at UNC. If he disappoints in the NBA, people will point to his time at UNC as an early indicator that he wasn't the player he appeared to be in Iowa. If he has a solid but unspectacular NBA career, people will look at his time at UNC as about par for the player he went on to be come in the NBA. If he becomes a perennial All-Star, people will wonder what happened to him at UNC, why he struggled between such a stellar high school career and a stellar NBA career.
Obviously, in that case, the problem will have been Roy.
Brian Zoubek on what was going through his mind walking to the free throw line with 3.6 seconds remaining in the 2010 National Championship game and Duke up by 1: "Fifty percent [of me is] thinking, This is what I've been dreaming of doing my entire life. Fifty percent I'm crapping my pants."