Absnerdity quit after 540 games (very late to quit!), whereas Peebs basically finished but had some weird loose ends left over involving peripherals.
I largely stopped tracking Twitch streamers back in 2021, since there's that big Google Doc with all of them. As you say, there are tons of people who started a project and bailed out after a small number of games.
On the Sega end of things at least one person finished their Genesis quest but, like most people who do this stuff, there was at least one sports game where I know it has a more definitive ending than what that person did.
Most of the successful completion projects I know of involve libraries of N64 size or smaller. Master System, TurboGrafx-16, 32X, Virtual Boy are all very achievable and have been done (not 100% sure about the Master System).
BTW @Reed Rothchild (just to bust your chops a bit) I need to be your personal Toys coach or something to get you one game closer to the full set. That game is easy -- I have no idea why so many people struggle with it, though you're far from alone in that!