I think based on the skills that these prospects possess we can say Johnson, or Toews etc...but utlimately its where they get drafted to, that could have the most to do with their upside or ceiling not floor. For example after Johnson, who is the consensus 1st overall, the next 5 players could all be centers. In my opinion whoever Washington drafts, with the intention of centering Ovechkin really raises that players ceiling in the league. Look at Colby Armstrong in Pittsburgh. He has been in the Pens system for years, and coincidentally, he sticks in the NHL when he is put alongside Crosby.
At this time we don't know for sure who will end where, so if I am forming a list of the prospects who could develop into great NHLers, I say...
Backstrom
Johnson
Little
Brassard
Toews
Kessel
Staal
Tlusty
Sheppard
Okposo