[drewbuschhorn]

I feel stupid saying this, but it was explained to me as being like light through a filter, like for spider man, Parker was always going to get powers (all things being equal) but because the trigger was spider related the powers \ way he manifests them are "spider colored", like light through a keyhole, different keyhole, different image, but same light source.

With regard to the X-Men, I think they imply the "present day" is a Cambrian explosion, that then settles down in the far future into the most useful powers becoming common if less godlike levels: immortality, psi, telekinesis, and any other boring wish fulfillment.