Final Fantasy X (Believe it or not, I don't outright HATE FFX. I think it's a terrible RPG, and I'm of the opinion that it fails miserably on the key point that an RPG has to offer, namely its story. The main character is an obnoxious himbo whose forcible insertion into the story offends me, but then again, it's not like the character who SHOULD be the lead (Yuna) is anything more than a meek romantic interest (despite very much not being that based on the story around her). But as a GAME, the gameplay in FFX is some of the best in the franchise. It's still got the ATB system, which works, but it has that order of movement list on the side that you can alter with Haste or Slow or whatever, and it feels like you have more impact on the flow of combat than a standard ATB. Plus, the leveling system is simple, yet dynamic. FFX evolves RPG gameplay in a really fun way. Blitzball's pretty good too, but it's a bit much to add on top of all the other mini-games you have to do for ultimate weapons. It's just that ultimately, the story IS what matters most in an RPG, and that's where FFX fails, unfortunately).
Haven't Played:
Metroid Prime (I've played it, but too long ago to remember, and nowhere near long enough to judge) Pokemon Mystery Dungeon Explorers of Sky Suikoden 3