Well, here are the guys I would list as being the best hitters from the 2008 draft:
Beckham, Tim - He doesn't get much love, as much as he should. Guys have become enamored with the 1b in this draft, and will regret the 5 tolls Beckham should develop at a premium position.
I wouldn't necessarily rank them in that order, but given my preference, the list would go like thi:
Alvarez, Beckham, Alonso, Smoak, Hosmer, G. Beckham
Hope this helps.