I looked at Roll20 stats two months ago and this is what i gathered.
On 4/8/24 0001 Hours (12am) there were 1000 games on offer (including mature only games) [At least this is how many games it showed 34 Pages. 30 games per page and the 34th page had 10 games.]
81% Official DnD systems (5e, 4e, 3e, 2e, 1e, od&d) [771 are 5E, 39 are 4e, 3e, 2e, 1e, od&d; 523 [511 5E] have a cost, 287 [260 5E] are free to play]
8.5% Pathfinder 1&2e (50 games or 60% PF1E, 35 games or 40% PF2E)
2.6% Call of Cthulhu (any edition)
1.7 % WOD systems
1.4 % Star Wars (any system)
1.1 % Savage Worlds
1.0 % Old School Essentials
.9% Apocalypse World Systems
.7 Traveler (any edition)
.6% Dungeon Crawl Classics
99.5%
.5 % All other games.
Now this is not representative of actual play since many games are TotM and perhaps are organized elsewhere (discord, reddit, etc) But its good to see the biggest vtt's numbers.