Man, I don't know how they made this game as good as it is. Aside from the last little artifact hunt at the end, this game is incredibly solid even today. The world is very fun to explore and it has a lot of memorable segments and boss fights.
I'm also very impressed by this game's storytelling. You can proceed through this entire game without reading a single word about space pirates, or chozo, or phazon, or you can get the whole plot told to you through computer screens and ancient walls. This sort of storytelling is incredibly good for this type of game, and I have yet to see a game do it better.