I doubt I remember some of these. Adventure was my first genre, but after that I don't know if the first one was the original Maniac Mansion or Secret of Monkey Island(I played a really large range of older and newer adventure games when I was introduced.
I was introduced to some genres far later. My first shooter was DOOM, and I didn't get another one until Goldeneye 007.
My first platformer was Sonic the Hedgehog.
3D Platformer: Super Mario 64.
Racing: Mario Kart, followed by Mario Kart 64. Never have been really big on the racing genre.
My first Japanese RPG was Poke'mon Yellow. Not sure if Western RPGs came earlier or later, it's one of those situations where I grabbed a lot of newer and older ones at the same time so the timeline is impossible to work out, between my unreliable memory and release dates not mattering.