In the "early years" I was largely playing whatever I could get my hands on, wasn't exactly me choosing. Platformers, sports, adventure, RTS, puzzle, managerial, 4x, even a couple of FPSs... Proper RPGs may have come in a bit later actually, oddly.
A bit later, among other things, I insisted on struggling with some RTS games even though I always sucked at them. That eventually changed, as over the past 10+ years the only ones I played were Homeworld 2 and Kohan 2, which are both somewhat different and more towards what I can play.
Been looking more into TBS in recent-ish years, after early on the genre pretty much meant HoMM for me and while I played them to a point and claimed to like them I was mainly just frustrated with 2 and 3.
Adventure games are one thing I was trying to play in the early-ish years but haven't touched in a very long time and don't care to.
Also haven't touched platformers in a long time and don't plan to. But even playing them initially may just have been a case of simply having them around, not a choice.
Also may be some 10 years now since the last 4X (Civilization 4, 2nd time around, just wanted to win again once). Early on there was Colonization, a couple of Civilization games, Master of Orion 2 and 3 briefly...
Otherwise, FPS games are one thing I was never keen on, but early on I did play 2 (Wolfenstein 3d and Quake 2) a fair amount, nearly finished Wolf actually. Then gave up the thought, only very briefly poking around a few more some 12 years ago, giving up usually after mere minutes and never touching the genre again since.
Oh, managerial games seem to be dropped too. There were a few football managers (CM, one FM and one other I can't recall the name of) plus Capitalism Plus way back, haven't touched anything of the sort in 10+ years. Then again, I do mean to play another FM, but with their Steam-only thing, no thanks, so keep putting it off at least till they have a change of heart, and probably forever at this point.
Also, long time since I last touched a sports game. But playing them (racing, pool, may add a bit of fighting here too, a winter sports one and a couple of odder things) early on was largely a matter of simply having them fall into my hands. Maybe an actual choice were the 2 FIFA games I played in the late '90s, maybe 2000 tops, but again none since.
RPGs remain a staple, but I'm actually wondering which the first proper one I played is and when. As I was saying, may have been relatively late, actually, so that in itself may be a change, but once I did play some, I stuck with the genre.
So basically, first whatever I happened to get my hands on (and I'm not counting the first 6 months or so when I had a ZX Spectrum clone, for which it was just dad getting a few tapes with whatever happened to be on them for me to poke at, before the first computer, or the NES clone with a bunch of included games which I played because, well, those were the ones I had). Then trying various genres, perhaps insisting a bit too much on a couple, till I found my place, and pretty much stuck with it since I was 18-20 or so.