Absolutely the best storyline in a game ever.  No exceptions.  Half Life 2 has an incredibly interesting and compelling story which feels more like a movie quality story than that of a game.  Just to emphasize how awesome the story really is, by the time I got this game HL2: Episode 1 was already out, I finished HL2 on Friday night and the next morning I made my mom take me to Best Buy to get Episode 1 cause I needed to know what happened next.  It's just that good.