Half Life 2 is a great game, at least in the opinion of the hordes of fans who waited years for it, and most of the "industry" - from retail to reviewers. But perhaps what we enjoy is the contextual change from Wolfenstein and Doom, the improvements that make sense within the FPS "paradigm" (or frame of reference).
A feature in Gamasutra; "Constraint is Design" interviews Katherine Isbister and Nicole Lazzaro, and gives the following quote
"Students who were not already fans of this genre felt really frustrated interacting with the Half-Life 2 characters. They expected even more interactivity and lifelikeness from them because of how good they looked"
So, what did you expect when you picked it up? And how did that change and mold your impression?