True. It was J.S. Bach who introduced the equal temperament. Remember his 'das wohltemperierte Klavier' (
http://en.wikipedia.org/wiki/Well_temperament)?
Indeed, the reason behind why the major scale sounds good is to find in the overtones. Actually, the lydian scale is the most stable, then follows the ionian (= major) scale. The stability of a scale depends on where the half steps are. This also influences the atmosphere / color of the scale. The more in front the half steps lay, the darker / more unstable a scale becomes. From bright to dark, stable to unstable: lydian, ionian, mixolydian, dorian, aeolian, phrygian, locrian.
Anyway, the lydian scale is the most stable 'cause: if you take all the overtones of C, you get:
C, D, E, F#, G, A, B
Of course not in this order, but if you re-order them, you'll get this. George Russell wrote a book about this: "Lydian Chromatic Concept of Tonal Organisation".