A lot has to do with playstyle. Someone who just wants to beat a game will be quicker than one who spends the odd minute to look at level details, to backtrack half a level because he thought there might have been an area he missed, or to just play around with the gravity gun.
Another example for me would be Doom3. My first playthrough of that game was about 20 hours.
If I just wanted to beat it, I could have done it in half the time.
This is one of the great things shooters of the past had that modern ones have lost: The confidence to let the player decide the pace. Modern shooters (well, not only shooters) are so densely packed with events that drive the action forward, that the player rarely is left to explore a level (or a setpiece, as it is called nowadays) at his own leisure. There is always that one squadmate telling you to catch up, or that headquarter guy that tells you to hurry up. Exceptions exist, but they are scarce.
So if one is used to these kind of games, it is only natural that he will blast through older ones as well.
So yes, HL2 is a 10 hour game, but at the same time, it can be a 15 or 20 hour game. It depends on the player and what he wants to do.
Another example for me would be Doom3. My first playthrough of that game was about 20 hours.
If I just wanted to beat it, I could have done it in half the time.
This is one of the great things shooters of the past had that modern ones have lost: The confidence to let the player decide the pace. Modern shooters (well, not only shooters) are so densely packed with events that drive the action forward, that the player rarely is left to explore a level (or a setpiece, as it is called nowadays) at his own leisure. There is always that one squadmate telling you to catch up, or that headquarter guy that tells you to hurry up. Exceptions exist, but they are scarce.
So if one is used to these kind of games, it is only natural that he will blast through older ones as well.
So yes, HL2 is a 10 hour game, but at the same time, it can be a 15 or 20 hour game. It depends on the player and what he wants to do.