Retro Gaming Enthusiast

Those are probably the best for a beginner to emulate.

Gen 1 is a bit rough. Graphics, QoL, bugs, etc. Easy to emulate and tremendous fun to play as someone who already knows the series well, but probably not a great introduction.

Gen 2 is better, but similar.

Gen 4 is complicated to emulate because of the DS. If you have a good setup for emulating DS games already they might be worth your time.

Gen 5 I would say is the best except it also has the DS complications. It doesn't use the second screen quite as much as Gen 4 though. And it's also my favorite as an experienced player.

Gen 6 and 7 are similar to 4, just with the added power requirements of the 3DS. Luckily the 3D isn't needed. If you have a 3DS, I'd say 5>7>6>4.

Most of the Switch games are vastly different experiences. SwSh are probably not worth your time. Arceus and Let's Go are borderline spin-offs. SV are worth playing, but still very different from most of the rest of the games.

Special shout-out to BDSP though. It gets a lot of hate, but I found them better than the originals and solidly mid for the series. They don't need a 2nd screen, touch, or most of the other hardware gimmicks that are a pain to emulate. I don't like the art style, but the graphical fidelity and QoL makes it much more playable for a beginner than the GB and GBA games imo.