If Fedor had signed with the UFC instead of Pride in 2002 and had fought for the belt in 2003 like he did in Pride, then I feel like his career would look like this:
In 2002, he signed with Pride and beat top 10 contenders Semmy Schilt and Heath Herring. UFC at the time had guys like Wesley Correia, Tank Abbot and other unranked random guys fighting in their 2002 events, so I can see him beating 2 of them easily to get a titleshot the next year.
Then in 2003 he would have beaten Timmeh for the belt because he was the champ at the same time Nog was in Pride. Then if he defended against the next guys that fought for the UFC belt, I feel it would have gone like this:
2003. Defense 1: Gan McGee (He looks like Stefan Struve. Went to Pride later and failed against Semmy and Herring)
2004. Defense 2: A young Frank Mir (Got GnP to death by Ian Freeman and KO on the feet by Brandon Vera. I can see Fedor doing the same)
2004. Defense 3: Arlovski (KOd by Rizzo already and almost got Kod by Timmeh in that fight too. Gets KO by Fedor)
2005. Defense 4: Justin Eileers (I don't know who he is either, but is funny how Fedor gets shit for facing Fujita or Goodridge while UFC title fights had guys like this)
2005. Defense 5: Paul Buentello (LMAO Fear the consequences)
2006. Defense 6: Timmeh again
2006. Defense 7: AA again
2006. Defense 8: Jeff Monson (Fedor actually beat him a few years later, he was already old in both fights)
2007. Defense 9: Randy Couture (Maybe the first one here that actually had a chance up to this point but Fedor would be favorite I feel)
2007. Defense 10: Gabriel Gonzaga (Gonzaga was a glass cannon. Werdum, JDS, Carwin and many other broke him easily. I don't see him KOing Fedor in 2007 so I can see him losing by KO or TKO like against 45+ year old Couture or decision like he did with Brendan Schaub)
2008. Defense 11: Antonio Nogueira (Just like in Pride. He fought for the interim belt while Randy was inactive)
2008. Defense 12: Brock Lesnar (The second guy that I see having a chance. Could take him down and do what Pezao did to Fedor 2 years later like he did to Mir in his second fight. Or could get scared after getting hit and run away like what happened with Carwin/Cain and Fedor would have given him the Gary Goodridge treatment)
2009. Defense 13: Frank Mir again (I still think that Mur was too inconsistent to beat Fedor even with all these years of experience)
2010. Defense 14: Shane Carwin (The third guy that could pull the upset. He would have had a really good chance based on Fedor already looking bad at this time like against Rogers, Pezao and Hendo. But Carwin also had cardio for 1 round, he didn't have good boxing, just HUGE power and Gonzaga nearly knocked him out. Most likely it would have gone like Fedor fight with Rogers IMO
2010. Defense 15? Prime Cain Velasquez (He loses here IMO). And I think he losses to JDS in 2010/2011 too. So I don't see him getting that belt back but would have a record of 14 defenses in the UFC in best scenario or 8 in worst scenario