The Half Life series are definitely my favorite games of all time, followed by (and maybe even tied with) Mass Effect. But yeah, take a look at the date of publish: 2004. Name one game that had extremely responsive AI, fully interactive physics, and extremely detailed textures like the ones illustrated in HL2. The atmosphere was immersive, and the story was great. However, I believe that you had to play HL1 to appreciate (but not understand) most of it... After all, it is a sequel, (which is what the 2 stands for) so why anyone would play the sequel without playing the first one is way beyond me. But I digress. The story is not some story-in-your-face type game that a lot of games tend to do. You actually have to pay attention to things. Even the smallest things like newspaper clippings on a bulletin board. And finally, the characters had more characterization than any other game I've ever played, especially around that time period. Enough said.