Kitad: TW2 alleged "shortness" is totally justified when you take into account that:
Goodmongo: There is never any justification for making the game short. And for all those so called reasons you list let me say that almost all other games fit most is not all of them yet are much longer.
Time to be honest with yourself. the game was short and it should have been at least 50% longer.
Of course its a good reason! Between a 60 hour game that has few locations, repetitive fetch quests, fake choices and tons of backtracking, and a 30 hour game that has beautiful hand-crafted locations, meaningful choices that really impact the game, unique quests and never a dull moment, I prefer the latter.
Obviously this takes a lot more effort and time.
Finally, more length in a great game is obviously better (as long as it retains quality), but its not automatic that length = quality. Portal and Portal 2 are prime examples.
That's not to say that Act 3 shouldn't have had more content, but that's a different story.