For me it’s first person puzzle games. I can think of maybe a dozen off the top of my head that came out in the last decade. I especially enjoy when they’re open world. The ability to just quit a puzzle that’s stumped you and go try something else for a little bit is incredibly refreshing.
Vehicle Combat games might be getting a comeback with the WH40k game and the Twisted Metal movie coming out.
Tempus Rising might kick off a C&C style RTS revivial.