Out of those listed, probably Greninja
I haven't even played X/Y yet but he just looks awesome and fun to play as.
However, despite your dismissal of his relevance, I'm more excited for Charizard being his own character this time. Since he was sharing space with 2 other characters in Brawl, I felt they cut corners with his individuality. Most of his attacks just felt like basic slashes and fire-breath attacks. I'm hoping they'll try harder this time to give him some distinguishable moves. It seems his Final Smash is his Mega-Evolution so that's a step in the right direction.
However, despite your dismissal of his relevance, I'm more excited for Charizard being his own character this time. Since he was sharing space with 2 other characters in Brawl, I felt they cut corners with his individuality. Most of his attacks just felt like basic slashes and fire-breath attacks. I'm hoping they'll try harder this time to give him some distinguishable moves. It seems his Final Smash is his Mega-Evolution so that's a step in the right direction.