Okay, here is why I do not like Half-Life 2.
It is a totally unextraordinary game that gets a lot more praise than it deserves. When I played it I found it to be completely and terribly boring, getting lost several times between fights because the game doesn't always give a decent indicator of where to go. The enemies are cliche and boring, too. Evil oppressive alien master race, Swarming alien bugs, and facehuggers "headcrabs" that turn people into zombes. The only fun I had was at the end of Episode 2, where you fought all the striders and stuff.
There, I gave my reasons for why I don't like the game I picked, now how about everybody else do so as well?