Critics praised Half-Life 2 for it's advanced graphics and physics. The Guardian gave praise especially to the environment design throughout the game. Most of the interest came from it's engine, and not particularly the gameplay. It's also seen as having a good storyline as most FPS games during that time lacked such a particular feature. It also has a unique character that everyone loves-- Gordon Freeman.
The environments were actually one of the things I enjoyed most of the time, especially Ravenholm. The graphics and physics did feel a bit outdated though. Have you tried the Black Mesa mod though? If it's good, I might try it, and see if I can get in on the story a bit better.
I only have Half-Life 2 for Xbox 360, and I've never actually finished it.
Oh alright, I had it on the PC. Never really got all that far through it.