To semi-quote Yahtzee on this one, "HL2 is a shining beacon in the swamps of FPS gaming" or something. Personally I love it and its the standard that I judge all other FPS's too.
I mean true, it sets the standards. It's just not as 'fun' as it could be. Maybe it just tried too hard to show off the engine, I'm not sure. Personally, I found SWAT 4 or Splinter Cell a lot more fun
Disclaimer: Any sarcasm in my posts will not be mentioned as that would ruin the purpose. It is assumed that the reader is intelligent enough to tell the difference between what is sarcasm and what is not.