Well trust me, I've seen more of Jamal Lewis and Shaun Alexander than anyone can imagine, starting with their freshman years in college. They are both great players. The thing that separates Alexander is the fact that he is ten times more durable than Jamal.
Alexander's running style is also much different now than it used to be. He used to go for the long touchdown alot more. Holmgren doesn't allow him to do that now, and I think that makes him much less effective. That's like telling Barry Sanders, "Now Barry, when you see a hole, hit it..just get the sure 3 yards." If Sanders had been told that, he wouldn't have been the back he was.
I'm convinced Holmgren ruined Alexander because he has completely taken away his ability to use his vision. And trust me, Alexander might have the best vision in a running back that I've ever seen.