I don't think that's true. I think there are a lot of developers that are either 1) unskilled/inexperienced and know it, 2) inexperienced, but think they are awesome, 3) experienced and skilled but believe themselves to be adequate, and 4) skilled developers that know they are skilled.

And I'm sure there's a whole range in between. Perception of ones skills don't always (may I say rarely) match up with their actual skills.

Personally, I think I'm average. There are moments where I think I did something smart, but they are fleeting. Is my perception accurate? I have no idea, I've never been graded by someone with far superior skills than myself. I'd consider myself insecure with my skills, but always striving to do the best I can.