Can't really top the Aldo/McGregor or the Rousey/Carmouche but for variety, I will also add:
- Machida vs Shogun 1: This is the fight that set the precedent for immediate rematches which IMO was one of the downfalls of the sport.
Upset wins are way less meaningful, the division grinds to a halt, the ex-champion either looks way over the hill (and has to switch divisions) or we're forced to sit through a trilogy. I can't even imagine the money that has been lost due to the laziness of this match-making over the past 15 years; it's no wonder the UFC has no stars left.
Bet they sure wish Sean O'Malley didn't have 2 straight losses and Max Holloway wasn't 0-4 in his last 4 FW title fights because gee... maybe people would still think they're credible if fighters coming off of a loss weren't fed to the wolves over and over again.
If Shogun has just got the decision he earned in the first place, rematches probably would have remained a rare occurence hell even Matt Hughes and Chuck Liddell didn't get immediate rematches FFS but oh no... Shogun gets one, then Frankie Edgar becomes the rematch machine, and now the sport is a lot less exciting.
- Matt Hughes vs GSP 2: As I just mentioned, rematches and spammed title shot were NOT common back in the day so it's crazy to think if Matt Hughes had somehow beaten GSP a second time, we likely wouldn't have seen one of the biggest stars/best fighters of all time rise to the top.
This one feels WAY less likely than most as Georges was even whooping Hughes in the 1st fight but if it somehow happened, it's highly unlikely GSP would have ever got a 3rd fight against Hughes who probably would have beaten Serra and continued on as champion. GSP might have even changed divisions!
- Chuck vs Rashad: If Chuck had beaten Rampage, he would have avenged all of his losses and we would have seen belt vs belt with Chuck fighting Dan Henderson at UFC 75. This could have been one of the biggest if not THE biggest fights in MMA history at the time but when Rampage won, "champion vs champion" was so unanticipated that the PPV became free on Spike.
With that being said, Chuck vs Rashad was an ever bigger what if. If Chuck had KO'd Rashad (who looked completely lackluster up until this fight), he would have gotten a title shot against Forrest and actually would have had a decent chance of winning the belt back. Having the biggest star in the sport at the time regain the title would have been a huge moment and even Chuck's last fight against Rich was seconds away from being a TKO win because Rich's arm was broken. Chuck's downfall had multiple opportunities to look somewhat less dramatic but it wasn't to be.
Joanna vs Rose: If Joanna had actually won this fight, would she have gone down as the WMMA GOAT? Who was really coming down the line who could have challenged her?
It's crazy to think that Joanna was on top of the world riding 5 straight title defenses and she ends up crashing down to earth to the point where she is practically forgotten now despite having close fights with Rose/Zhang after this. Rose has 2 wins over the current SW champion too yet feels like she's been borderline retired for a while... what a bizarre career/life she has had.