1. Mighty Mouse
2. GSP
3. Volk
MM is underappreciated by so many fans. Dude's ability to make reads and exploit openings is incredible. MM had such good awareness, e.g. that walk-off left knee KO against Moraes in the rematch because he set it up and timed it perfectly. His training videos with other fighters is such a great series, e.g. that recent one where Arman called him a genius.
GSP fought smart and very consistently, was a master at utilizing the jab and takedowns to control fights. I do wish he took more risks, but he had a long reign because he rarely made mistakes.
Only reason I listed Volk 3rd instead of higher - and I think his game is so well-rounded and frustrates opponents - is his lack of patience in taking the big fights at the right time. He could have had an argument for all-time GOAT had he not gotten TKO'd in 2 straight fights.
I don't have eye-poker on my list because the constant fouls / threat of eyepokes and testing positive for PEDs so many times shows he didn't mentally believe he could win without cheating.