I never said that Kane would be #1 over all the other forwards......But I honestly think that Alzner is a level below many of the forwards in this draft group (including Kane).
I saw another article on HF ranking players in the WHL.....Alzner was ranked behind Cody Franzen (drafted 79th overall in 2005), Kris Russell (drafted 67th overall in 2005), and Ty Wishart (drafted 16th overall in 2006). Which leads me to believe that if Alzner was a available in 2005 or 2006 he would not be a top 10 drafted player.....but in 2007 he is? That shows more of a weakness in defensemen in this draft than a strength for Alzner. I still think Alzner will be selected in the top 10. But he is not deserving of a top 5 pick in this years draft.
Depends what league you are talking about. Also look at the talent surrounding the prospect and evaluate that. Kopitar was playing in a much more competitive league on a below average team in Sodertalje. Same with Zetterberg and Datsyuk in Europe. They were playing against men, meaning they have to be pretty mature and well-rounded to be playing at such a high level.
Now when you compare a forward to a defenseman, you have to look at the impact the forward is going to bring to the team compared to a defenseman. The defender obviously draws on the tougher assignments, usually logging more minutes and playing in many various situations, with the man-advantage, with a disadvantage, protecting a lead, shutting down a sniper, etc.
You don't have to be flashy to be successful, especially if you are a defenseman. Look at the high and low end of the prospect. Alzner will be an NHL defenseman and regular roster player, and it is always a positive to select a prospect who will be an NHL player, just as all of those defenseman you listed.
I won't be disappointed if the Kings selected Kane and I won't be disappointed if the Kings selected Alzner. I want to see them draft an NHL player.