When I played this game 10 years ago, I was completely blown away and playing it again today just confirms how ahead of it's time it was (or perhaps still is). It effortlessly blends action/adventure/exploration/rpgesque elements and creates an alien world more complete and persuasive than the likes of even 'Avatar'. It is also, unlike many of the old classics, still a breeze to play thanks to tight controls and a sharp UI.
Basically apart from the graphics (and thanks to fantastic art direction, even they still retain much power) the game has not dated in the slightest and you really have no excuse not to give it a try.