>>54292099FRLG
Just the original game with some updates and new content. Cannot go wrong.
LGPE is an odd case, since I like some parts of it, but not others. They removed the safari zone, and added these gym requirements, replaced Green/Blue with some gay forgettable nu-gen helper ""rival"", removed the added content from FRLG so there's now just no post-game, and though the graphics are about the best we'll get from Gamefreak 3D I don't like the artstyle. But, I do appreciate the even further updates to the mechanics, the following pokemon, being the only game where you can ride on your own pokemon, I know people sperged about the GO catching but I didn't mind it as a little bit of alternative gameplay from the rest of the series. Overall, I could replay it, but I wouldn't really recommend it.
RBY is of course worth playing if you never have, but since they didn't really know what they were doing yet, things like bag space make it kind of a pain compared to further versions. It's also not really what you'd consider a well put together game on the technical side with the amount of ways to trigger bugs or break the game, but at least that won't affect most people doing a normal playthrough.
I guess the GSC/HGSS version also counts, but at least in GSC Kanto is so butchered it isn't worth considering. I don't remember what HGSS Kanto is like.