Motivated Instant Classic
The only downside is despite the new engine and story, the game plays it rather safe by making it very similiar to it's predecessor. This downside though also keeps Half-Life to it's roots of what makes it so great so it's really a double edged sword that still leaves one hell of an impact on you.
With it's key points on modding, great story and gameplay and overall fun experience, Half-Life 2 is a game that'll make you keep coming back.