I don't know what most Michigan fans believe (i.e., that he is "the best coach evarrr.")
I do know that most Michigan fans believe Harbaugh is a significant upgrade over Hoke and Rich Rod.
Personally, I think that Harbaugh is a very good coach, but he hasn't really proven anything yet. For me, it is a combination of many things . . . not just Harbaugh, but also position coaches, quality of players on the team, support services, physical resources, and a fair amount of luck.
I think that if you are consistently recruiting like Meyer has (in the top 5), you are going to be very good. However, there are a ton of wildcards that can't be predicted. No one knows injuries. No one knows who will turn out to be a superstar. No one knows who will flame out due to academics, or substance abuse, etc. No one knows when a coaching staff is going to throw away a winnable game by not adjusting properly to scheme, weather, etc.