Most video games these days let the player pause the story-driven cinemas, or even offer an option to skip the cinematic interlude of they choose when a button is pressed. Some instantly skip when you press start, others just bowl them over for the next action scene. Other have hover text stating, "Press this button to skip." What's lacking here is consistency.
Of course, you can pause a movie when you're watching it at home, but playing these mega-blockbusters video games these days is sort of like being at a theater, only worse. It's the equivalent of if nature calls midway through the feature, getting might actually skip past that block of the flick for everyone.
I honestly don't know what would happen if I had tried to pause one of those story bits in Gears 3. It's not like it's in the manual, mostly because Gears doesn't even have one. Maybe the start button does pause them, but how can I know? If you miss one with key info, it can require replaying significant portions of the level design.
There are other consistencies in gaming, the right trigger acting as fire, left aiming down the sights, analog sticks controlling movement, etc. Not all control schemes would work for all games (switching the smaller trigger for X in terms of reloading is always a toughie), but it's a developers right to change up as they see fit.
But gorgeous displays of CG prowess? Why would any developer not let someone know how to pause that in case of a phone call, pet interruption, significant other bickering, or sandwich urges?