One of the greatest RPGs ever.
The first thing you notice in Tales of Symphonia are the graphics, which are, simply put, superb. A few anime cutscenes are interspersed throughout the game that really add a lot and are beautifully drawn. The entire game utilizes an anime feel that really makes the game feel right.
The game's battle system, while a bit untraditional, works perfectly. It takes away the feeling of leveling up as a chore and makes the entire game fun! New moves and combos are unlocked throughout the game, and you can play as any of 8 characters.
The sound, again, is superb. ToS contains some of the best voice acting I've heard, and the soundtrack was good enough that I went out and paid $60 for the 4-disc soundtrack.
Where Tales of Symphonia really blows away the competition, though, is the story. It takes you from laughing so hard you fall off your chair to staring, stunned, at your TV to crying like a baby and everything in between. That's what I call a good RPG!
ToS also contains the ability to play through the entire game with up to 3 friends simultaneously. I never tried it with more than two, but that was a blast! The only flaw with multiplayers is that the camera follows player 1 in battles so other players could end up off the screen for a bit.
Have a gamecube? Buy Tales of Symphonia. Simple as that.