This is more of a gee whiz question since I its all based on preference, but does it seem that there are more songs based out of the A and E major key (and relative minors) than any others? Granted we can all find good songs that were written in another key, but why do you think people choose A and E when, from a theory standpoint, something such as C can be worked around easier in solos and such. Personally I think its because the first two strings on the guitar are E and A, so its easier to resort to those nice open chords.

Please let me hear your comments!