Yes. But for all of those you need to buy hardware that can actually play the games. (A few hundred for a console, a thousand for a PC). The promise of game streaming is that you can play AAA games on the low-powered laptop or phone that you already have.
There's a few possible business models for streaming. E.g. with PS Now you have to pay a subscription, you get access to a games library, and can only play the games that are part of the library. (Not other PS4 games that you own). Or GeForce Now which in practice requires a subscription (the free tier is only 1 hour at a time) and allows you to play a limited set of games as long as you own them on the right platform (e.g. Steam). Xcloud seems quite likely to just be sold bundled together as part of another subscription.
So the free tier of Stadia should have been interesting due to not requiring a large up-front investment, and not requiring an ongoing subscription. Which at least at this moment is unique. Or rather, would be unique, because 9 months after the announcement it still has not launched.