I dont really like Vincent, and I have said a lot that he doesnt feel like a real Corleone to me, so maybe thats where you got your intro from. Like other people have said, you never see him actually show his inteligence. Sonny was a smart guy, he just had too short of a fuse. You never see any of Vinnie's brain matter. He just seemed to appear out of nowhere and then he became Mike's successor. Maybe if his scenes showed other sides to him (maybe not focusing so much on his affair w/ Mary) I might feel diffrently.