Also, I would never use your service because of DRM. GOG doesn't do DRM and always has many indie games on sale, which seems like a better value prop? I don't think the Spotify analogy works because games are already very cheap. I have a large backlog of games I'll never get around to playing, and so does everybody else. Being able to choose from millions of songs on Spotify is way better than having to buy individual albums, but I don't need access to a large game library.
Maybe this is another "less space than a nomad" kind of comment, but my intuition is that indie games are mostly played by older gamers who are happy to just buy a game they want to play. Go to gog.com and see how many games you can get for the $100 a year you plan to charge.