What I had enjoyed most while playing through XY for first time is finally gaining access to player-customization feature.
I've been wanting to see such a thing be introduced into this series for a very, very long time, and as I've stated in other threads before, it was sort of a dream come true to see this happen at last. When I'd first gotten my hands on it, I had spent a decent amount of time messing around with options and whatnot, all of which were fun; it's great.
Though, it is slightly disappointing to not see this feature make it into Omega Ruby and Alpha Sapphire, at least in some fuller way. Hopefully, this is just a temporary thing (as May and Brendan are already-established characters, I could see why they would restrict us from personalizing them), and they will bring it back in future title releases.