Microsoft: 9/10 - The only thing I'd like to see improvement on is having even more titles available, but I understand that this isn't entirely Microsoft's fault. I'd also love to see Dreamcast support at some point, but I'm not holding my breath for that. XD
Nintendo: 7/10 - Nintendo at least seems to put a lot of effort into the re-releases it *does* bother with. I'm not super-fond of Nintendo Switch Online, but it's functional and costs very little. Plus, the Classic Edition consoles are well-made, and I can still access a lot of older games on 3DS and Wii U. I wish they'd bring that sort of effort forward to Switch, though.
Sony: 5/10 - Sony used to be incredible in this regard. I don't own a PlayStation 4, but my PlayStation 3 will remain connected to my TV until there's a better alternative for playing my digital PlayStation (1) titles. While I do like the fact that we occasionally see re-releases of older games, I hate the fact that they're not free if you already own the original, and the emulation is pretty shoddy.
By the way, one thing I'll say about Microsoft's approach is that it does a much better job of recreating the experience that you remember. It's sort of the argument that people have had about the PlayStation Classic actually hurting people's perception of the games they used to play by making them worse. On the other hand, with Xbox One (X especially), you get better performance than you originally had, as well as a higher resolution with X. I think you stand a better chance of enjoying those old games, because they hold up better as good as (or better) you believed they did, albeit maybe with slightly weirder controls.