Ali is unique.
Silva is unique also.
I believe, when people will look back at Silva's career, 20 years from now, they will talk about him pretty much the same like they're talking about Ali right now.
The thing that separates these two however is: Ali had HUGE rivals when he was fighting: Frazier, Foreman or Norton.
The trilogy with Frazier is EPIC. And their 3rd fight - *The Thrilla in Manilla* - is (probably) the most famous boxing match in the history of the sport.
This is what Silva is missing honestly - a rivalry with a tough competitor!
SIlva will no doubt go down as one of the best MMA fighters of all time - at the time he retires he migh be considered the best tbh - and it will take some serious performances from the current MMA fighters to surpass Anderson Silva.
However i still consider Ali much bigger.