I don't see Bush having a huge amount of success in the NFL. I think he'll end up as a good player but never a great.
The comparisions to Barry Sanders are ridiculous. He's never shown Sanders type moves. I have seen some Gale Sayers talk and that does seem comparable but remember when Sayers played he was demonstrably faster than any defender. Bush won't be.
The lack of defenses he's played against the last two years will show when he can't run away from people on the next level.