Based on the past two or so years of game?
Surprisingly, not the First Person Shooter. This genre/subgenre is not exactly fresh, but games like Overwatch and Doom 2016 showed some of the ways that the genre can still have some variety. There are still plenty of them, but they're not too saturated.
Hell, even the MMO isn't too saturated nowadays. It was for ages, but with WoW now at a more reasonable playerbase of 5 million or so, you've got room for Final Fantasy XIV, Korean MMOs, The Old Republic, EVE Online, and many others with over 100k active users. And with the number of new MMOs lower now, it's working out.
I'll go with the Open World genre. Especially Action Adventure games. Since early 2015, we've had Assassin's Creed Syndicate, Watch Dogs 2, Mafia 3, Ghost Recon Wildlands, Far Cry Primal, The Division, Horizon Zero Dawn, Breath of the Wild, Metal Gear Solid V, Batman: Arkham Knight, Just Casue 3, Mad Max, and the ocassional pseudo-RPG like Fallout 4 which is fairly close to this category. And those are just the ones I could think of without proper research!
Love and tolerate.
