I'd say it has to be First Person Shooters. Mainly because that is the genre which 1) I am generally best at & 2) I do most of my multiplayer socializing with.
It doesn't have to be a specific FPS type. I enjoy the Mil-Sims, Run & Guns, Tacticals and even crazy (see: DeepRock Galactic).
As well, I've enjoyed Single Player and Multiplayer FPS titles, but generally would say I lean more towards Multiplayer because the social aspect of gaming is huge for me.
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