1 of the many differences between GSP and DIaz is Diaz isn't afraid to lose. He is fine with taking an ass beating if you actually fight him.
Anderson could easily play the game like GSP. He could easily stay at range and pick guys apart (Aside from Sonnen who charges you) but every other fighter he could pick a part all fight from range. Using jabs and a variety of kicks. He could win 50-45 or 50-44 against guys like Okami, Franklin, Marquart and so on. But he doesn't. He wants to put on a show, and wants the finish. He could easily play the keep away game somewhat similar to Machida but with more jabs and leg kicks. He could make sure no one hits his chin. But he doesn't. Because he is a fighter.
Guys can fight however they want. GSP is popular as hell and is the champ. He makes good money. But that is some of what DIaz is saying....in the true essence of it, he isn't a fighter at heart. He doesn't care about the fans because he knows his legion of fans will follow him no matter what....because he is a brand.
Guys like Diaz, Anderson, Hendo, Shogun, Fedor, Nogs, Wandy, aren't afraid to lose a fight. That is what made/makes them awesome.