I think the best way to establish this thread is to separate retired fighters and also weight classes.
But I'll go with Gsp. Not because he was flashy and exciting with his wins. But because he did it in 2 weight classes, I know his fight vs Bisping was cringe but he won vs a real middleweight champ and dominated quite well at ww.
I still think when Serra took Gsp out it was nothing short of awesome. For that, I'll always be a fan of Serra.
For me, 2nd place goes to Anderson Silva. He had an incredible run against a murderers row.