I'm going to say that Ellenson is the least exciting prospect who's currently projected in the top 10. He's talented, but he hasn't managed to score efficiently, and his defense is poor. A decent comparison for him is Sullinger (although Ellenson has better quickness + handles; he has more potential as a face-up threat).
Ellenson: 21 PER, .53TS%, 16.5TRB%, .74 AST/TOV, 30/104 3pt, .75FT%
freshman Sullinger: 30 PER, .59TS%, 20.1TRB%, .75 AST/TOV, 3/12 3pt, .70FT%
Basically, Ellenson is a marginally better shooter, and Sullinger is better at everything else. 30 vs 21 PER is a huge gap. I'd say that Ellenson's ceiling is roughly as a skinny Sullinger with a 3pt shot, which is pretty good; but his median outcome is significantly worse than Sully, and there's almost no chance that he'll be nearly as good as Kevin Love.