You're making a loaded comparison though. Phil Kessel is an 18-year-old this year. Crosby was a 17-year-old last year. The difference is a gulf.
The difference in terms of development between 17 years old and 18 years old is massive. Same thing from 18 years old to 19 years old, and 19 years old to 20 years old. If Kessel is as good as he is, then he should be able to beat the numbers of a 17-year-old, even a 17-year-old as good as Crosby, since Kessel is 18. Any scout will tell you that. Anyone who knows anything about player development will tell you that.
Case in point Team Canada this year. There are 10 19-year-olds on Canada's roster. Of those 10, only four were remotely in contention last year. (Barker made the team, Bolland was a late cut, Dubnyk, I believe, was the first goalie cut, and an injury cost Chipchura a place on the checking line). Even if we didn't have the all-star team, thanks to the lockout and the strength of the 1985-born players, those are the only four 1986-born players on the team. Guys like Pogge, Boyd, Comeau, Blunden and Pouliot have made tremendous strides since their 18th birthdays. Pokuluk, I believe, is the only 19-year-old not playing a key role.
The closest thing to a fair comparison that we have is Kessel as a 17-year-old at the WJC vs. Crosby as a 17-year-old at the WJC. Can't compare their performance in league, since the Q vs. college isn't a fair comparison. (Although both played against opponents three or four years older). 17 vs. 17 is the only age vs. age comaprison we have. I'd love to see how 17-year-old Kessel would have faired vs. 17-year-old Crosby at the WU18 (now that would have been a fantastic gold medal game), but Crosby was still in the Q playoffs.