I was introduced to D&D with one session of Holmes Basic. After that is was Basic Moldvay. Played all other editions of D&D over the course of the last 41 years. Did play a few science-fiction games along the way but they never stuck. Always went back to D&D.
Currently, I haven't played D&D since May 2020. My default system is AGE by Green Ronin. I GM Fantasy AGE, Modern AGE and The Expanse AGE in rotation with two groups.
Not looking to get back into D&D nor are my current groups.
You may get different results if you post this question in the TTRPG General section.
My introduction to tabletop games was playing DnD for the first time in 2018. I've purchased and read other game systems, but haven't gotten a chance to play any of them, besides a short CoC one-shot (which I had a lot of fun with).
Started with Moldvay Basic in 1981 (the Erol Otus cover for the box set is one of two iconic images for me when I think of TTRPG). Quickly transitioned to Gygax AD&D (aka 1E) after my family moved (the Dave Trampier PHB cover is the second iconic image) and played that throughout middle and high school. Our group also played Champions frequently with some other games occasionally sprinkled in (Gamma World, Top Secret).
After a long hiatus, I tried 3E and PF but found them too "crunchy" for my taste, skipped 4E, gave 5E a decent try (played for a few months) but have generally found that modern games just don't do it for me.
So, now I don't play any longer as I am primarily interested in older versions of D&D or more niche systems that no one else seems interested in playing. I could try to find online games, I suppose, but am not really a fan of the remote gaming dynamic.
I was introduced to RPGs by the Mentzer Red Box. D&D is still my main games (AD&D, 5e and a little bit of OSE currently), but I play other games. In the last year: CoC, Scum & Glory, Ironsworn and Symbaroum.
For folks my age and older who started as kids we had to start with D&D because that's all there was for a window of time in the mid 1970s. We tried lots of other games as they came out - Traveller, Runequest, Gamma World, Boothill, Gangbusters, CoC, etc., but always came back to D&D for our longer campaigns.
Assuming that AD&D counts as D&D started with 1e, played some Red Box, but 2e was my (A)D&D, played it enough that I got burned off the game, moved to Rolemaster, then GURPS and WoD. Only came back to D&D towards the end of 3e, literally bought the books about 3 months before 3.5 came out, quickly drifted away from 3.5, tried pathfinder found it made the bits I disked about 3.5 more prominent, so left both games played other things until 5e came out, discovered that I liked it and stuck with 5e from there on in. Though I do play other systems (though not Rolemaster or GURPS because I played them too much back in the day). Now about a third of what I play is D&D, the other 2 thirds are other stuff, mostly non fantasy stuff, since I find D&D works to cover my fantasy itch.
I was introduced to "D&D" through a medieval-fantasy live action roleplaying game. Then brought to the table to the game that was "like the LARP, but we sit around a table and play with pen, paper, and minis".
Now I play both D&D and other RPGs. Now that the kids have grown, maybe I'll start LARPing again. Probably to run out of breath after the first 15 seconds of combat...
I started with the white box set in 1976 whilst at school, and have played all editions since though I largely avoided 4e. Back in the day, I also played Runequest, Traveller, Bushido and a bit of Chivalry & Sorcery. Even played Bifrost if anyone remembers that. More recently, I played a lot of Pathfinder but became a bit disenchanted due to bloat ( my opinion only, no aspertions cast) as well as Rogue Trader and WFRP, both of which I enjoyed immensely. Lots of talented people in the world, putting out great games.
Advanced Dungeons & Dragons (First Edition) all the way back in 1993. Never "switched" to 2e, since I'd been using 2e books fairly seamlessly with my 1e books for years-- but I did have a torrid love affair with Player's Option.
I have played a whole Hell of a lot of other games since then. I'm not going to attempt to name them all.
If by "still playing D&D" you mean still playing the in-print and supported edition of D&D published by Wizards of the Coast... the answer is no, I haven't really played that for a few years. If you mean actual old school D&D, the answer is yes, and if you're including Pathfinder and unofficial retroclones of D&D, the answer is also yes.
I'm also still playing a number of other games regularly: mostly Alternity and Street Fighter, some Barbarians of Lemuria, and various Cortex games.
I started with D&D and prefer D&D. I try to make D&D do what I need it to do, and it generally does.
I have played other games, and enjoyed them, but havent stuck with them, so didnt count them.
I am resistant to learning new gaming engines. I would have to know ahead of time, that it does things I care about better than D&D does, before I would make any effort to learn a new system. Things that might tempt me would be a better ability score system, along with a strong reputation for customization and gaming balance.
I am looking forward to the new Cortex, and will check it out. I am unaware about how balanced the system is.
Hence: I was introduced through D&D, and only play D&D.
I started with D&D 3.5, started GMing with D&D 4E, began experimenting with other systems (Savage Worlds, Pathfinder, WoD, etc) shortly after. Got into D&D 5E, fell out of love with it. While I do still play a few D&D-adjacent games, I haven't played a game of D&D proper in years.
I used your last option, because all the rest would, from where I sit, be deceptive. I absolutely started with D&D (around 45 years ago now), bailed out on it for decades, came back for a while with the 3e period, and then bailed again. I'm manifestly uninterested in any version of D&D proper (though I'll at least give a tip of my hat to some parts of 4e), but on the other hand I've played both Shadow of the Demon Lord and Pathfinder 2e in the last few years, and wouldn't write-off 13th Age out of hand. So I don't know if they count as "D&D" for the question.
I play all kinds of other things, many of them non-fantasy.
I started with D&D (Red box, 1E, 2E, 3E, Pathfinder, 5E) and have played Star Frontiers, Gamma World, Villains & Vigilantes, Marvel Super Heroes (both FASERIP and SAGA <--- the best superhero game I've played), DC Heroes, Call of Cthluhu, Vampire: The Masquerade, TMNT & Other Strangeness, Amber Diceless, Mutants & Masterminds, Star Wars (d6 and d20), Hong Kong Action Theater, Supercrew and countless other one-shots and dabblings I cannot recall. But the truth is, we always come back to D&D
I was introduced to RPGs in 3rd or 4th grade by a kid who was 14 or 15. The original Top Secret. I was immediately hooked. Throughout grade school I played Top Secret, Traveller, 2300 AD, Gamma World, Twilight: 2000, Marvel Super Heroes, Battletech, Cyberpunk, Star Frontiers, Star Wars, and more. And, of course, D&D.
I'm in my 40s. In adulthood I fell out of the hobby for many years as an active player but never stopped collecting. I jumped back in about four years when my daughter was born and I needed a social outlet.
In 2021 I've played a lot of D&D 5E. I have also played (or am planning to play) Marvel Heroic Roleplaying, Night's Black Agents, and D6 Star Wars.