That's probably because he can't walk on water.
I know what you mean and I generally agree. He was good - probably better than Nonu was towards the end (due in my mind to Nonu playing non-stop rugby for over a year) - but he certainly wasn't as good as people hyped him to be. From the beginning people seemed desperate to compare him to players like Daniel Carter and Jonah Lomu - the reality is he wasn't THAT influential. For all the hype and so on - the result was him playing ten minutes in the RWC semi-final and final combined (in which time he got a yellow card).
For me - what he was, was a good player with a lot of natural potential. Regardless I don't think the NZRU should have signed him in the first place as it sends a very wrong message, was literally a **** you to every other inside centre in NZ the amount of oppertunities he got - resulting in loyal players like Hosea Gear getting no time in the RWC (despite being a better winger than SBW ever could be), the loyalty of whom stays in NZ despite being overlooked in his best form, while SBW leaves (and people want him to return for the next RWC, I mean ffs!). I dislike what SBW stands for - but as a player he was good. Not what the media made him out to be, but good none the less.