Some people here are saying it's the best game ever (not just best fps). TBH I think for pure depth of gameplay and story, Deus Ex 1 leaves it in the dust. Without question. But that's just my opinion in any case.
There are a couple of things that really get old in HL2 quick. The physics puzzles (how many are there and how 'setup" are they?) and the jumping to get from one area to another, or a combination of the both. Insanely old gameplay mechanics. The scripted side however I did like. Very good for keeping interest. I mean my girlfriend doesn't mind watching me play and that's saying something.
I kind of think as a pure fps and just on the gameplay side, Far Cry is slightly better. HL2 just seems restrictive to me after playing FC. Far Cry's bad points though are the cheesy cut scenes, dialogue, story and voice acting. The ending was an anticlimax also. I really was expecting some sort of boss to fight, but instead you just cap a guy with 1 bullet and the game ends.
They all have their ups and downs.