IX is the best in my opinion. Why?

Characters: Zidane was an amazing lead. I had the gloomy, withdrawn "badass" types that run around with big swords. Zidane was just a normal, friendly, cheerful guy that people can actually relate to. Vivi was awesome. I've seen people say crap like how he's emo and depressed and stuff (not that you can blame him), but he keeps going and trying to beat it and make things better for himself and for his fellow black mages. Garnet was also a fantastic female lead who actually did a good bit of growing throughout the story.

Setting: it's an actually fantasy game, not cyberpunk or futuristic. When I think RPG, I think fantasy, not sci-fi. Unless it's in very small amounts, leave that to FPS games, I don't want it in my RPGs *glares at Xenosaga*

Kuja: Best. Villian. Ever. He makes for some gorgeous eye candy, plus he's extremely manipulative. I find a villain who can manipulate countries into war and manipulate souls to be much more interesting than the generic badass with an uber sword and anime haircut who goes around slicing and dicing.

Plus the game just has a certain charm to it that I love.