iRacing, Project Cars 2, Assetto Corsa, Raceroom Racing Experience, rFactor 1 and 2
I'm sure there are others I'm missing
Yep, and GTA V races modes with 32 players apparently isn't part of the conversation either. Let alone other genres that have been doing MMO for years and years, in the hundreds even.
EDIT: I also like how posters instantly forget about input latency and round trip back to the screen. Say Stadia go 250-1000 multiplayer games, that is still huge latency, round trips and will affect game experiences regardless of the in game/graphics processing of the cloud. They'll side step some of that with predictions, perhaps even AI, machine learning and digital avatars versions or even full blown replacing player inputs with server overrides as tick rates sync/resync etc.
At the end of the day Stadia is interesting tech but given current limits and lack of success in games that offer 40-250 players in one match Stadia will likely succeed with allowing a few months or mobile subscriptions to dive in for less cost up front. Oh and YT integration.
For core console I see them sticking with Sony/Xbox offerings over Stadia, perhaps PC players will complement their away from home activities but isn't Valve working on similar already too? I wonder who core PC players would prefer? To me, for now, it's a segment similar to mobile gaming. Long term if Internetworking tech allows Stadia could become huge.
EDIT 2: Some of the developer comments about one platform to develop for are misguided as well. Over time Stadia will have the same hardware/platform revisions to develop targets for. Just as PC and consoles have done and will continue to do.