If you’re buying for collecting sake then buy the rarest one but if you’re buying then to also play and appreciate some honest gems from the past then a Super Famicom probably is the best ratio of fun to nostalgic.
The Genesis. Playing the mini recently illustrates how much games have changed since then. The system had some RPG's, but many of its classics are shorter action games that take a few hours to beat (or under an hour if you memorize them).
It's just the furthest you can get from today's sprawling, everything and the kitchen sink games. Surprised how much fun I had with that change of pace. Maybe check out one of GB's Genesis streams for a taste of what's out there.
Personally, I'd go with the Neo-Geo if I could afford both the console and some games. It's the system I'd spend the most time on when going to the video game store and playing their demo units lol. It was the console that completely out of reach console I dreamed of owning as a kid. If I can get a solid well paying career, it's probably the first one I'd buy after replacing my SNES.