The reason Silva fought Bonnar is because the previous main and comain fell apart. They needed a main event fight and Silva offered his services.
He is the GOAT (we're talking a small list of possibilities: Fedor, GSP and Dan Henderson.....if you want to put Jones in there now, I can see that).
He's the best because he's been unbeatable. He was getting his ass kicked with a busted rib in the first Chael fight and ends up choking him out at 23 minutes of the 25 minute fight. He crushes Chael in the rematch and has done the same to Franklin, Henderson, Belfort, Okami and all but a few of his UFC opponents.
Plus, his style makes for impressive action. Saw it last night like the Forrest fight, great head movement. Against Okami, knocked him down with a jab.
He wants GSP next at 178-catchweight. Everyone else wants him vs. Jones, but neither of them want to go through that.