@ 30 fps, it's better for a game that has a slower pace, which means it's not likely an action based game. Assassin's Creed titles, is hardly all about continuous action.
Obviously, this won't fly for the shooters out there.
60 fps is the minimum for Shooters, and may become the norm in the future, with the advent of 4k and beyond. UBI has been experimenting with 60fps for awhile now, and have found they can increase and decrease the action in a game without increasing fps. With the current direction of the industry, it almost looks like they are in fact, trying to get away from hyper fast fps gaming.
Even monitor development has pretty much slowed up from how it was 2-3 years ago. So it is possible, we won't be seeing anymore 120+hz monitors later on. "4k@ 60fps or bust".