dude
fitst off the game took 12..yes....TWELVE years...I bet they had enough material to make it last that long
second if Crysis 2 has modular chapters (which it probaly will) I'll take a 4 hours cut gladly as modular chapters add sooooo much replayability
Also......it's also all about how much tension the game creates. Dead space 2 clocks in about 9 hours to finish on an average non NG+ playthrough...but it feels a lot longer because of the tension you are always experiencing