X/Y are awesome. It's new in many, many ways, but there are plenty of reminders of generations past. The "bump into a wall" sound is unchanged, and for some reason, it really made me feel good about the whole game.
The music is improved, with battle themes for all different scenarios: Wild pokemon battles, trainer battles, gym trainers, gym leaders, Team Flare members, Flare admins... and so on and so forth.
Fully animated 3D models of all pokemon, and their attacks. Awesome.
I love the newest starters. Well, the grass one, at least. He's like a friggin' paladin.
The way the legendaries figure into the main storyline isn't as fleshed out as in previous generations, but the trade-off is a world that is richer and feels more populated than ever before.
You can catch Mewtwo, and it isn't bloody *&^%ing impossible like I remember it from Red/Blue. Bust out a Doublade/Aegislash (steel/ghost type) and you're all set to wear down Mewtwo through sheer attrition.
It's going to be a bit of a shock to jump from Red/Blue straight into X/Y, but you'll get *RAMPANT GODDAM SPOILERS* not too far in so I think it's worth the initial adjustment.