I'm not particularly interested in cloud gaming as it is, forgetting multiplayer already having issues with server latency that has a real effect on games, putting it into cloud doesn't actually help that. Of course, the companies who do make these services are not interested in this experience or preservation, only to make a buck.
So for ported titles (aka things on PC or console already) there is no no big whoop about it. When it comes to exclusive things, that is where the problem lies. There are games that were on the Gaikai platform before Sony bought them that are lost forever. Some of them have physical client versions that are unusable. All online only or required titles have this same fate eventually, they will get lost to time or be unusable at some point.