AFAIK there is one and only,
totally legal service similar but not exactly like this: Console Classix.
2018 news article with more details about legality:
https://arstechnica.com/gaming/2018/08/can-a-digital-lending-library-solve-classic-gamings-piracy-problem/
edit: just sharing some notes and experiences
- Console Classix comes with a modified emulator.
- When you select the game, you download the ROM from their server.
- Doesn't seem to be encrypted. ROM is present in memory (no file is being made)
The sad truth is that licensee of video games (usually the publisher, the developers and/or someone else with sharing it up for a given percentage) wants profit. They don't get money from people playing these and they don't really seem to catch the original customers, the players wishes...
I would really love a service like Gefore Now, where you can verify your purchases of supported games and play it through streaming, running on a cloud computer. There is no ROM sharing. The service also grants security to the titles, in case someone would try to make an illegal copy of the game running.