Sometimes people who are very intelligent can express things or talk in a way that may come across as snobbish etc. but I think that quite often it is just a difference of communication and understanding. There are a few that think they are better than others because of their intelligence but I don't think this is the common way of thinking.
As for selfish, I'm not sure if a personality trait can be linked to intelligence. It is interesting to think about though. I mean, I'm going through my head of the people I know that are really intelligent...and one comes to mind that I know can be selfish, but whether that is connected to their intelligence, I don't know.