I'm guessing that is because of the short time to complete, yes? I certainly wouldn't call that the most important thing.
Then your definition from Gamespot:For the most part, a game's value score is an indicator of the game's longevity. It represents how long you'll be able to both play and enjoy the game, and it also signifies how much replay value you'll get out of it. Breadth of gameplay options and overall volume of content both weigh heavily into this score. The retail price of a game can also figure into the value score, as can the presence or lack of similar, competitive products in the market. Finally, the overall quality of the game has some impact on its value, so, for instance, a bad game that's extremely long is still probably not worth playing.
Clearly they take much, much more into account than length. Something can be completed in 2 hours and still get a 10 from Gamespot in the value department if you keep playing it again.
HL, the original, had value unheard of in the action game genre. I hope HL2 does.
I haven't played Hl2 or Riddick yet. I hear Riddick was absolutely amazing on the Xbox, which shocked me, being a license and all. I'll check it out, but truthfully the subject matter isn't all that interesting so I might not dig it all that much.