I think a lot guys think they are smarter than they are and they think they are uglier than they are.
And girls do not like intelligent guys really. They like guys who are easy to communicate with. This ease of communication is often confused with being intelligent. You could have a phenominally smart guy, but he cannot hold a conversation, he will be unattractive.
Infact, I bet every guy a girl likes, the girl thinks the guy is "intelligent".
This misleading notion in a girls mind, leads them to think they find objectively intelligent guys attractive, when in reality they consider the people who they like as intelligent (whether they really are or not).