I've heard, before the pros, he beat Bute and Andre Dirrell. I watch the fight and the kids is impressive. Good eyes. Good balance. Good power.
If I was on his team, I'll call out Cotto and Alvarez at 154. If not call them out, try to get on their undercard.
At middleweight, Geale, Pirog for their titles would be great for GG. Peter Quillian would also be good exposer.
At 168, Dirrell, Pavlik or Abraham.
Against any of them, I'll give GG a good chance.

Sidenote:
I should be a promoter