See, when I pick up an FPS game I want story. I thought HL1 was a little too much action and a little too little story. HL2 I thought managed the balance perfectly. I'll admit some components in the level design were irritating, but on the whole I thought the game was extremely well done. In a stroy-driven game, linearity is a must... or at least, in that type of story-driven game where you are essentially playing through a novel. Take a game like Deus Ex or System Shock 2, however, and you get a little more variability in paths and outcomes (for anyone who hasn't played either of these games, I'd say they're probably my favorite two of all time. Deus Ex edges in slightly above SS2, but only slightly).
Halo was a great game too - yes, some repetitive levels (God, I HATE the Library), but on the whole the story was excellent. And really, I'll take a fantastic story with level flaws above a technically well-designed game with no story ANY day.
On those grounds, I'd say HL2, HL1, and Halo were all excellent games. Especially Half-Life 2. There's so much in it. I can understand why some people wouldn't like them, though.
However, if anyone here slams Deus Ex or System Shock I'm going to have to break out the baseball bat. =P