These GOAT threads never end.......OK, I'll bite
These are the only fighters that have a claim to this title IMO
Jones
GSP
Anderson
Fedor
DC
Jones is the most dominant MMA fighter of all time and it's not even close. He's fought the best of the best and only a few times has looked to be in any trouble. With that said, he's a cheater so he clearly cannot be the GOAT. We don't know when he has been on or off the juice, so it's hard to say if he would have lost to Gus or DC without PEDs.
Fedor was really good, but definitely not on the same level as Jones, DC, or GSP. I think it can be argued that he was as good as Anderson, but his lack of legit competition really hurts the case. Fedor also became mortal almost overnight once he started fighting in the States. I have no problem with the fact that he was most likely juiced to the gills in PRIDE because everyone else was too. What I do have a problem with is the fact that he got absolutely handled by Bigfoot and looked like shit against Rogers and Arlovski other than landing a big bomb when he really wasn't that old.
Anderson was great. He was about as dominant as it gets during most of his run, but I feel like he really benefited from favorable matchups. I think that fight with chael really ruined his chances at GOAT status for me. Yes, Chael was on the juice, but Silva probably was too. I don't think the rib thing was that big of a deal. I think Anderson would have had problems with power wrestlers like that, but he didn't really fight to many in his career because they were in other weight classes.
DC is the second most dominant fighter in this group. Other than the Jones fights, he has looked pretty unbeatable other than a brief few moments in his MMA career. DC also seems to be a clean fighter, which really ups his stock. The only thing that hurts DC's claim to this title is that he lost twice to another guy on this list. Peds or not, that looks bad.
GSP had an aura of invincibility about him in his prime. He was boring as fuck, but you just knew he wasn't going to lose. I don't think anyone has ever fought at the same level as GSP in this sport, and he is probably the most well rounded fighter of all time. He wasn't as dominant as Jones, but I feel he fought better overall competition during his run. The biggest issue with GSP is the lack of finishes. I have no idea if he was a cheater as far as PEDs go. He looks dirty as fuck, but he never got popped.
Conclusion:
GSP is probably the GOAT at this point in time, but there is no clear cut favorite in this list. They all could arguably be considered the GOAT, as a case can be made for all of them. I will say that this conversation will be much easier if Khabib defends his belt a few more times and beats Tony dominantly. It will be hard to dismiss an undefeated fighter with over 30 wins that was never even challenged in his prime against multiple elite fighters as not being the GOAT.