That is, genres you used to avoid like the plague, but now are a fan of. Or vice versa? (inspired by GothikOrk's thread)

Personally I used to like a few sport games like tennis and baseball on the nes, and I think there was a soccer one on
dos that I had the demo of. But now I have 0% interest in any sport games (excluding certain types of motor sport). Well, perhaps if a really good rugby game were to come along I might check it out.

Genres I had no interest in at one point were RPGs with turn-based combat, and any JRPG. Fallout and Chronotrigger respectively quickly cured me of that affliction.

If indie counts as a genre, then that too was something I avoided, naively thinking that amateur 'basement' games couldn't be any good. Gish started to cast doubt on that idea, but it was World of Goo that killed it outright.

City Builders

used to despise them now I love them

I mainly avoid all multiplayer games for several reasons (time consuming, bad community, more frustrating than fun, will be unplayable one day...). This mostly concerns FPS (CSGO, Overwatch, CoD, Battlefield...) and MMORPGs.

Years ago, I was on the top competitive scene of Team Fortress 2 with thousands of hours invested. I realized this was pointless, community was awful and I was not enjoying the game anymore.

Same with World of Warcraft, I enjoyed the game a lot (played during vanilla and BC) but I can't play a game which will disappear one day. Sometimes I wonder how people who have characters with 10+ years will react when the game will close (and it's just a question of time). Same with Guild Wars 2.

Now I only play games I can enjoy alone "forever". This mainly includes RPGs and strategy games (especially Paradox wargames).

But those game are time consuming too, that's why I try to discover games well suited for short gaming sessions (mostly roguelites like Dead Cells or Enter the Gungeon). I play them when I want, I don't need to play 4h a day to stay better than anybody else and I will be able to play them in 10 years.

That's my philosophy of gaming.

More out of life circumstances:

I used to love complex 4X games and flight simulators (not the real grognard stuff, more like the old Microprose and DID games).
Nowadays I simply lack the time and thus patience to actually learn these games, so I avoid them.

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What city builder showed you the light? :) SC2000?

yes, but that took me a while.
I had that game when it came out and hated it. Only in the last few years did I really come to love it.

I found SC (1) incredibly fascinating, although at first I only knew the C64 version. Later I got it for the Amiga and it was a jaw-dropper when I first started it.

Some of the best gaming experiences I had was with TF2, but only when both teams were more or less equally skilled. Those long drawn out matches where you desperately, and successfully defended the front line were always epic. Especially playing as engineer and seeing how everyone keeps using your strategically placed teleporters. And to kill all the would be spy saboteurs/assassins. I don't think I spy got me even once playing as an engineer. Just had a 6th sense to sniff them out :)
What put me off of the game though was that it became more and more common for lots of players just to go free-for-all and not even attempt any degree of teamwork. Then it wasn't fun at all :\ Well, that and the constant large updates were too much for my connection to keep up with.

As for your point on WoW, personally if the game was still good and I had the time I would still play it today (played for a couple of months around Cataclysm's release). Of course it will probably cease to be one day, but I'd be sure I will have had my fill long before that time comes. Oh yes me too though I can't remember on what system I played the first SC. It was unlike anything I had ever seen. But yes, by comparison SC2000 was simply jaw-dropping. I remember calling a friend of mine shortly after starting up the game for the fist time, just to tell him how amazing the game was! It held my attention, I believe, right up the point I got Caesar 3.

I did a 360 (well, almost) on FPSs.

Used to be my favourite genre when I played Woflenstein 3D. I loved Doom, then Rise of the Triad, but when I played Duke3D and Quake I no longer was that big of a fan, and by the late 1990s I almost completely gave up on them. I preferred RPGs for the story.

Until a friend recommended Half Life. I wasn't too keen on it, but told him I'd try. I was so out of touch with FPSs that I played it Doom style: Right hand on arrow keys, left hand on space/Ctrl/letters. No mouse aiming. And got quite a bit into this game before my friend corrected me. I loved that game, and still consider it one of my favourite games of all time. I remember finishing it with 1 HP left.
That game, together with Max Payne and Alice got me back into the FPS/TPS genre. I still love it, and enjoy these games both with good/decent stories (like Half Life 2) and mindless shooting (like Serious Sam) or anything in between. I've since played both old 2D ones (Blood, Shadow Warrior), which I still play without mouse, and new ones.

Yeah, quite a few I suppose.

I used to love RTS games, one of my favourite genres, but I just can't really get into them any more. Old ones, newer ones that I've tried, they just don't grab my interest like they used to. I must have put 100s (if not 1000s) of hours into AOE2, Dawn of War and Red Alert 2 (among others) but I don't enjoy them now.

I used to love City Builders but struggle to get into them now (I think this is down to the fact that I like to look up perfect layouts and then things get a bit boring as you generally just repeat the same tactic and the same layout level after level). I still keep buying them though XD.

I've been back and forth on FPSs a few times, used to love them, didn't play them for years but have gotten back into them a little now.

Multiplayer, I enjoy but I find it hard to get the uninterrupted time required to play a game you can't just stop and pause at any time... that and online communities are pretty shit and toxic these days so I mostly don't bother.

Interesting, if anything I think duke3D rekindled my interest in the fps genre. I think I had only played wolfenstein, doom and blake stone up to that point, which were all pretty abstract in their level design. Duke3D on the other hand had recognizable real world locations, e.g. a movie theater complete with a bigscreen, projector, toilet stalls etc.
I thought that was just impossibly cool at the time.

But yes, Half-life just blew everything out of the water (except for Unreal that is:))

And the Alice games are also way overdue for a gog release, along with FAKK2 while we're at it.
How about the Blizzard RTS offerings? Or the ones less 'traditional' like the Homeworld remake, or that homeworld-in-the-desert game? Or Dungeon Keeper, Evil Genius?

I definitely get your point on city builders, which is why make a point of not looking up or using what are considered optimal layouts. I'm technically still busy with a Caesar 3 playthrough, and I make a point of trying something new every level, and I'd say it's worked pretty good thus far. I'm hoping to use all the knowledge I gain this way to create a final supercity in a scenario before I move onto Pharoah.

Well I never owned Warcraft 3 but played it often at a friend's when it came out, and I got it dirt cheap recently at a second hand shop and found it wholely underwhelming. A complete disappointment compared to my memories of it.
I haven't played Warcraft 2 or Starcraft in years (though I believe I got Starcraft when Blizzard gave it away free a while back, but haven't installed it yet), and haven't played Starcraft 2 at all.
I don't think I've ever played Homeworld beyond a few minutes with it years ago.
Dungeon Keeper still appeals, the first one at least, but I don't really see that as an RTS like most RTS games.

I try really hard not to but I'm a perfectionist and what things to be just right... when I finally get around to playing the Chinese one I'll have to make sure not to look anything up or spoil myself with 'perfect' layouts.

MMOs. I used to hate WoW, then I liked it (girlfriend), then I hated it again (broke up). So I guess I did a 360.

Same here. Oddly, it was the Fallout games that started changing my mind as well.