Given the strong DIY ethos among OSR DM's and cross-pollination between the clones & TSR era rulesets, the idea of a "dominant" OSR game kinda misses the point of what a lot of people are doing. I own print copies of 9 retro & neo clones and usually run 1e, S&W or my own version of OS D&D, which cribs from multiple sources. All in all, that's not atypical.
Hearing DM's saying things like "Well, I'm running S&W right now, but it's so heavily houseruled and mashed up with other sources, that I don't really call it that, anymore," is par for the course.
I said that for my 3e game. I'm maybe a bit of an odd case. I'm not old-school, but I am old-fashioned. I have no interest in systems from "yore", and I'm not even very interested in specific D&Disms, but my playstyle is very firmly rooted in that mash-it-up, do it yourself, GM ruling based game. In terms of tone, B/X has always been the closest to what I wanted, of any D&D game. But I still never liked the rules, the arbitrariness, the specific D&Disms, etc. of B/X. I was "done" with D&D
before 2e came out, rather than because of 2e, as was commonly voiced near the launch of 3e.
3e worked quite well for me, but I had to ignore a lot of the examples of how to do things like calculate DCs and whatnot. I always saw them as samples of what kinds of things to think about, not "laws" that needed to be strictly followed. In fact, I frequently scratched my head at all the comments that people, who otherwise seemed to approach my own tastes with regards to playstyle, couldn't make 3e work for them.
What finally drove me away from 3e were things that I never liked in the first place, and finally had enough of, but many of them were inherent in earlier versions of D&D to some degree as well. Tactical minis combat? Tired of it. Not what I want. The magic system? No interest. Not my idea of enjoyable fantasy. The focus on dungeon-crawling? Never want to see another dungeon again.
To me, it was the very D&Dness of the 3e system (and its derivatives, like 3.5 and Pathfinder) that turned me off. Therefore, my interest in the OSR wasn't likely to be very high, because my disenchantment with 3x D&D was completely different than the disenchantment that led to the OSR. But I did, however, see an awful lot to like about the "old-fashioned"-ness of the OSR, even as I had no interest in the "old-school"-ness. The DIY attitude was always how I ran, and the stripped down rules started to feel more and more attractive as an easier way to get there.
In the end, I settled on m20 variants as my system of choice, probably for the foreseeable future. 4e only magnified the aspects of 3.5 that I already didn't like, and Pathfinder took aspects of 3.5 that I didn't necessarily like but didn't necessarily mind either, and made them more burdensome to excise or ignore. The OSR was full of games that harked back to games that I never liked in the first place, often with rather smug harangues on how the hobby should be done (Matt Finch's OSR primer, as well as lots and lots of posts on Grognardia and lots of lots of posts by OSR fans
here, frankly, which contributed to my lengthy hiatus from the site.) m20 is an interesting system, because it has a lot of d20 in it, but it has a lot of OSR in it too. I still find the OSR a fascinating movement within gaming, even if it isn't really my cup of tea, so I tend to keep half an eye on what's going on in that regard.