Its not the worst game in the world, just as all Valve games get hyped to death, this is getting some serious negative hype.
It sure is a let down after all its promise, and it sure is far worse than Stalker, Crysis, Fallout 3, and even Clear Sky. But... I had more fun in my short playthrough than I did in the whole of Half Life 2!! You have to play it as a blast, forget the open world, it has not been used to its full, and the economy and way you progress by "unlocking" weapons is pure console shit. With a real economy, better story, and improved AI this could so easily have been game of the year.
It fails mostly because of comparison with its peers.
I knew I would get one game for Christmas, luckily it was not this one, I'll play it for free when my mate admits defeat. He is currently still plugging away at this one!! My advice, if you did get this game, give it a chance and forget your expectations.... it's *cough* average.
If anyone bothers with it, it just may be modded into a superb game, I'll be checking back on that aspect.
PS. The game I did get was GTAIV, and I know that once past the excessive DRM that is a good game. Before installing it, as weird as it sounds, I am looking to crack it just so I can remove all the Rockstar and GFWL crap that goes with it. I'm currently too busy having fun in Fallout 3 though!!