Khabib
McGregor
Mighty Mouse
Stipe Miocic
Rich Franklin
Rob Lawler
Chad Mendes
Discuss
The reason why I chose these four is because of how incredibly controversial they are. I'll add some more guys who fit into this category.
Rich Franklin had a great career. For his talents and work ethic, he became a champion. He isn't an all-time top 5, but definitely an all-time top 10, especially considering he is one of the most important figures in the rise of MMA in the US.
Robbie Lawler also had a great career -- or rather, a good career, with a great resurgence. After being in the fight game so long, to be able to climb back up and become a world champion by fighting some brutal wars is impressive. Robbie is definitely an all-time top 10 in his division, and probably an all-time top 5 as well.
Conor's career has been extraordinary so far, because of the interest and money he is generating. He is a great striker, has an exciting and intriguing personality, but his career is still young.
Mighty Mouse is often overlooked because, well, he is really little. But he's also a great fighter, one of the best in the world. It's both a shame and yet understandable that fighters in lower weight classes don't get nearly as much attention as their talent would seemingly dictate. He's a top 5 all-time great in his division for sure.
Stipe Miocic is a solid fighter, with a fantastic work ethic, and a great attitude toward the sport. He is just entering the prime of his career, in my opinion. I suspect he'll go 4-1 or 5-1 over the next 2-3 years, likely cementing a spot for himself within the all-time top 10 for heavyweights.
Chand Mendes' career has been good, but that doping violation definitely taints it. But he's a solid fighter, a very good wrestler, and not as appreciated for his talents as he should be.