I found a few 'normals' who are quite intelligent actually. (even though they don't listen to metal nor classical music)
I don't think normals are that different from us. Everyone is going to have different life-experiences/upbringing (And of course, different genes). All of these factors are intertwined in a very complex dance in the development of a personality, and it is very difficult to say, specifically, what makes someone 'normal'.
If I assume that a normal person is someone who is able to adapt and survive while possessing an 'average' mind and body; then, a 'normal's' thought capacity could be quite close to the same level as any one of us (maybe even greater on many occasions?).
Then again, are they really "normals"? I don't think that listening to metal and classical music should be the sole criterion for labeling someone as 'normal'.
Plus, I don't think I would like to meet someone like one of 'us' since we have a tendency to be snobbish, depressed and elitist. On the other end of the spectrum, I dont want to meet someone who is as dim as a cow and annoyingly smiles all the time while making light of everything, either.
I think the 'normal' person can be quite sound of mind since they fall in between these two extremes (overly cynical versus overly optimistic) and it seems that there are more 'un-normal' people than 'normal people.
Because of what I have described above, I find the whole idea of labeling people as 'normal' quite simplistic, narrow, and ridiculous since there are fewer 'normal' people than we really think.