I agree with you except to add that if Sonnen did happen to level things (and I sure hope he doesn't), a decider could potentially be UFC's biggest ever attraction.
MMA fights tend to be quite 'cagey', both guys are afraid to commit because it doesn't take much to get knocked out with the tiny gloves. There are a few though, mostly in the lower weight classes though because they don't hit as hard, Chan Sung Jung vs Leonard Garcia I was really good. Horrible technique but a good exciting brawl. Maynard vs Edgar II was also great, I haven't seen the 3rd one yet but I hear it was good too. Obviously these aren't up to par with Ali-Frazier for me anyway but that is probably a little bias on my part.
I don't think he is discussing a great trilogy but more a hellacious fight that goes right down to the wire. Mind you, Edgar-Maynard III was give and take and went into the 4th round.
II fits that pretty well, and there'll be arguments forever over who should've got the nod. And III was touch and go for Frankie up until the finish. Combine them into one fight and that's a hell of a roller coaster.
Also just thought of Pettis/Henderson. That fight was back and forth the whole way and it easily could've gone either way, right up until that kick.
In terms of action, high-level quality of fighting and historical significance, Penn-Hughes 2 is a good watch. Two ATGs close enough to their primes that the fighting was tremendous quality. And it finished with a satisfying and definitive ending, even though not everybody was impressed by the performance. :hat