Well, in general RPG's are basically mostly story-based. The cool part about FFX IMO is the battle system. You can switch people in and out, and depending on who is in, you have different abilities in relation to the enemies. However, the battle system does get annoying towards the end of the game, especially when you know you can beat every enemy with minimal effort and you get into a fight about every 5 steps.
Also, it has the cool minigame blitzball that is just totally awesome! I must've spent at least 30 hours playing blitzball alone. Better yet, when you start a new game, the blitzball league evolves differently. Thus, it's a whole new sub-game each time!
Anyway, I'd equate FFX to Final Fantasy: The Spirits Within except that you get to play as the characters, it lasts longer, and the story is a hell of a lot better. Also the music is top-notch for an RPG (they don't recycle the tracks for each area, so you don't get tired of the music).
Although FFVI (III for the SNES) is still the all time best, FFX is probably the 2nd best.