THer's also GeForceNow, from nvidia - it's been around for a few years now.

I've used it for Prey 2 (finished) and The Witcher 3 (in progress) and I'm really happy with it. It's still in closed beta (although I think it's available commercially somewhere in Asia(?)), but it's a no frills product that does exactly what it says.

There's no platform play, though (like the Stadia integration with youtube and special Stadia dev framework etc), but that's an advantage to some.