Coming from an Xbox 360 and a PS3 owner, HL2 is one of the best games to ever grace the original Xbox.
What amazes me is that this game is capable of being run on the original Xbox. The graphics are outstanding, and can even compare to next gen games. Its awesome how Valve was able to pack this masterpiece of a game into a measly Xbox disc. HL2 is a technically amazing game, and I will explain why.
PHYSICS: HL2 has the best physics ever made in a game to this date. End of story. You are able to pick up object, throw them, watch them break and bounce of walls realistically. Shoot an already dead in the foot and watch his leg jerk around. This game has the best physics engine you can imagine.
GRAPHICS: Okay I am going to be completely honest here. I bought The Orange Box for the 360 and played HL2 all over again. Then I wanted to experiment to see how much of a difference in graphics there was from the original Xbox to the next gen consoles. No joke, I didn't notice a difference between the two. The 360 version was even running on 1080i, and the original Xbox version ran on 480p. I played through the whole beginning of the game, comparing the textures on walls, the lighting effects on garbage cans and other objects, and I didn't notice a bit of a difference.
OTHER: There is only one problem with the original Xbox version of HL2. The framerate suffers right after you are done loading. But thats it. I enjoy playing this game on the original Xbox more than anything because I love basking over it's sheer amazingness.
This game is a true masterpiece.