Of course he could have become a star. It's pretty much universally accepted that it was shitty booking that killed him. With an easy-to-market cosmetic look and big impressive power moves, all he really needed was good, consistent booking and he could have eventually broke out into the main event (whether he would have been able to sustain interest as a top player in the long term is another question), but that's where the WWE fell short. He had tremendous momentum going into the 2012 Hell In A Cell match with Punk but then look at how it all went down hill from there - he failed three times in a row to capture the WWE Championship from Punk, got repeatedly trampled on by The Shield, lost the Royal Rumble match after a rather unimpressive showing, lost to Mark Henry at Wrestlemania, then suffered an ill-fated heel turn and jobbed to Cena in a feud over the strap. Forfeiting his match to The Miz like a pussy was just the icing on the cake.
The thing with Ryback is, he's a fairly one-dimensional type of persona and wrestler. He's not the best talker and he's not the best worker, so he has to rely almost entirely on his impressive physique and the handful of big impact moves he has to carry himself and get himself over with the audience. With a character like that, you have to get it right from the get-go, or else you ruin any sort of chance of ever getting over to a main event level. Look at how Goldberg was booked in WCW. He debuted, said very little, destroyed countless wrestlers and had a long undefeated streak and got over big in the process. Now compare that with Ryback's booking and it's easy to understand why Ryback failed.
