that's a bit too much about only x and y... and these are music tracks rather than songs...

since I've yet to encounter too much of x and y, i'll just list my 5 favourite pokemon songs:

I wanne be the very best (season 1 opening)
It's a whole new world (season 3 opening - jhoto)
Unbeatable(season... who knows.. Advenced Battle or Challenge - Hoen)
Black and White
We will be heroes(it's one of the sinnoh openings)

I don't have any preferred music, I love them mostly, except diamond and pearl battle scene, it's crappy and annoying one for me.