How can I gently tell someone who thinks he's really charming that he is actually really creepy?

I know this guy who thinks he has quite a way with the ladies. He thinks he has smooth moves and lots of great lines. In actuality he is creepy, says things that are inappropriate, and has yet to get a second date with any of the some 25 women he has seen (met via internet dating sites). Can you think of a gentle way I might be able to tell him where his problems seems to lie?