Emulating the classics, or playing them on real hardware might be the way to go, and not getting things like a Switch 2 or later (maybe a Switch, since you seemingly own the games you have in those cartridges, and not some DRM-heavy license where the developers will revoke it at any one time).

Pokemon uranium is playable on PC, I don't think it works in consoles. Played it long time ago so I don't remember how good it is though.

I don't know how easy it would be to find though since Nintendo shut it down.

Pokemon Infinite Fusion is probably one of the best out there imo

My favorite rom hacks are mainly Emerald based.

Been enjoying Pokémon Odyssey, which is a bit like Made In Abyss crossed with Pokémon. It’s got a full quest log and a huge dungeon and great story to explore. I haven’t played too much of this, but I have loved the hour or two I played through.

I also enjoyed Pokémon Scorched Silver, which acts as a Johto sequel and has a huge dex of mons up to Gen 9.

Because I’m a huge Emerald fan I have to shout out Pokémon Seaglass. It’s got a retro artistic feel to it. All the sprites are basically demakes and go back to the classic Gen 2 style. There are also battle backgrounds, following Pokemon, dexnav, and some balance changes, such as letting the Light Ball work for Raichu and Pichu.

Odyssey is the most unique, but Seaglass is really polished. Scorched Silver feels like another mainline game just with a huge dex. It still retains some of the level cap issues for the original GSC games I believe.

Romhacks:

• Link to the Past Randomizer - Generates a shuffled ROM with all chests and items swapped around, sending you on a wild goose chase through Hyrule trying to find everything required to beat Ganon. Has a LOT of settings to play around with.
• Link to the Past/Super Metroid Combo Randomizer - Like the above, but with both games combined into a single ROM using some elaborate witchcraft. Certain doors take you from one game to the other, and the item pools are shuffled together so you'll have to go back and forth between Hyrule to find Metroid items and Zebes to find Zelda items. It's a bit imbalanced by the fact that LttP is a much bigger game than SM with far more items and locations, but I recommend playing through it once for the sheer novelty.
• Celeste Mario's Zap & Dash - A metroidvania running in SMB1's engine. As the name suggests, it's heavily inspired by Celeste and ports in mechanics from that game.

Standalone fangames:

• Panel Attack - Open source clone of Panel de Pon/Tetris Attack/Puzzle League/Puzzle Challenge/oh my god Nintendo please pick a name and stick with it featuring netplay and modding support.
• AM2R - Another Metroid 2 Remake. Do note that I've heard a big 2.0 update is supposed to be coming soon, so you may wish to wait for that.