Kanye again trying to gain some publicity
Britney won because she has a bigger fanbase than Rihanna and more people voted for her. That's it.
The same thing happend with 30 Seconds To Mars and Tokio Hotel. 30 Seconds To Mars won 2 awards (Best Rock and Video) over more successful acts too because their fans voted for them. But of course, he only talked about Britney
He also said that Lil Wayne should've won Ultimate Urban. But there's a little problem about it: Lil Wayne is a LOCAL star. He's only successful in USA.