Mark J. Rebilas-US PRESSWIRE
Reasons People Criticize Him: He's a cheater; Dana White says he's the greatest of all time but he's not, he doesn't (often) speak English in America, he ducks challengers, he's the champion of a weak division, and on and on and on...
The Facts: Silva haters won't be dissuade by logical arguments, so to get into a large discussion about why Silva doesn't suck would be a waste of time.
Nevertheless, the facts speak for themselves. He has the longest UFC title reign of all time, the most successful title defenses in the history of the company, as well as the most consecutive wins in UFC history.
Keep in mind, these records weren't set against guys like Zuluzinho or Hong-man Choi. Yes, there were some wins over subpar guys in Silva's undefeated UFC streak like Patrick Cote and Thales Leites, but there were also wins over talented fighters like Dan Henderson, Rich Franklin and Forrest Griffin (a former Pride champion and two former UFC champions, respectively).
Silva hasn't truly lost a fight (meaning been finished/lost a decision—it's a joke to count the DQ loss to Yushin Okami when discussing such matters) since 2004, when he got submitted by Ryo Chonan in a once-in-a-lifetime flying scissor heel hook.
Final Verdict: You can hate the guy for not speaking English to the fans/media on most occasions despite the fact that he's demonstrated that he can speak English. However, saying he's not a skilled champion or only looks so good because he fights bums is just plain wrong.