It depends. When a game sets itself out to be a game with a wide-arcing, epic story, then no, instant gratification won't work. A good story has Action, Downtime, Action, Story Building, Action, etc. with those downtimes beig either huge lengths of time or small ones.
However, if a story that sets itself up to be an epic, and the story arc goes ACTION ACTION ACTION ACTION ACTION ACTION downtime MOAR ACTION like Black Ops felt like it did, it makes the story less immersive, and worse, in the end. When you're always focused on the action, you can't really grasp the story that's unfolding around you.
Does that mean that constant action and instant gratification is always a bad thing? No, not really. A game can just decide to be action all the time, and that can be very enjoyable, due to the challenge and fun of the gameplay itself.
But when you really look at it, the games that are widely regarded as the best (Mass Effect, Halo, Uncharted, Fallout, etc.) usually follow the Action-Downtime-Action kind of setup. It's what's natural in our lives (school/work, then leisure, then school/work), and it's what we're used to.