>>718356760 (OP)
there are three layers to what could count:
cancelled games in various states of completion, discontinued subscription or GaaS games, and standalone releases that are lost
>cancelled
Earthbound (nes), Bioforce Ape, Shantae 2, Steambot Chronicles 2, original version of 6 Days in Falujjah, etc
many cancelled games are eventually released or leaked in some form: EB was auctioned off and then eventually released in English officially, Bioforce Ape's prototype was found in a garage iirc, Shantae 2 Risky Revolution enjoys a recent release
alas, Steambot 2 is likely gone forever, and 6 Days was 3 days from release when it was delayed and reworked from the ground up
>GaaS
see SKG threads
>lost standalone releases
half the indie scene for the Macintosh is lost with no known backups, some PC98 games are insanely difficult to find if backups exist at all, a lot of 80s PC games could be gone forever
there was that time 70 rare games were leaked only to be taken down by the rare games mafia. It was tough, but Anon managed to rescue 100 of them