Gotta be honest, even though I grew up during Goldberg's time period, I didn't really watch WCW at all. But from things I've seen in the archives and whatnot, I'll give my best shot.
As far as importance in WCW, he was extremely influential. He caught on at the right time and was booked the way he should have been booked. Unbeatable. He was WCW's last ditch effort to beat WWF. The NWO was oversaturated and Goldberg was what WCW needed. So, as far as WCW goes, Goldberg meant everything. But, when it comes to WWE, I don't feel that he translated as well. Goldberg's whole deal was that he was an unstoppable monster. Once he gets beaten and washed out, it doesn't matter anymore. (That's what has happened to Ryback.)Yes, his arrival was huge. Doesn't mean he was good in the long run. The same thing could be said if Sting came over. Goldberg had been one of the few big names WCW had that had not come over yet. So when he did come, it was monumental. His influence was there. But, WWE was not a good fit for him, in my opinion.
As far as wrestling ability, I can't support him. He's a good power guy. I'll give him that. But he's sloppy. I still can't let go of the concussion he gave Bret Hart. The spear and jackhammer combo was a great moveset for him. They looked painful as Hell. But other than that, I never felt like he could keep my attention in the ring.
Overall, I agree with Horrorfan. What is happening to Ryback is exactly what would happen to Goldberg if he debuted now. He debuted at the right time to catch on. Other than that, I don't think he would be remembered as well.