This is going to be a hot take but out of all of those, HGSS would be my choice for removing from existence. It does everything right at a baseline level Pokémon game but it doesn't do anything that other games in the series don't do better
>gym leader rematches
Emerald had these and in level tiers, too. It also didn't NEETwall you.
>Battle Frontier
Copypasta'd from Platinum
>Following Pokémon
Overrated feature with no real benefit other than occasionally getting items
>General soul/Pokémon feel
LGPE is praised for this
>Pokéathelon
Contests were better, Musicals were worse. Plus, Stadium 1/2 mini games are moe fun
And in addition to
>the worst Safari Zone in the series
>not fixing the level curve
>introducing the box legendary hunt postgames into the series
>not having random online battles
>not being compatible with Pokémon Ranch
>small features for the sake of having small features like Cameron, the shiny leaf crown, having dressing up again from Platinum for no reason, Buena's Password, etc
I see as a game that doesn't have a lot of direction and relies too heavily on the fact that it is a remake that does a lot more. With no shred of irony, it is the most "insists upon itself" game on the series. I don't think it respects the players time when it comes to all of the time gated events and really its highpoints are all of the cool mythical events. The Pokéwalker was cool too but if they had just waited for the 3DS for that idea, they would have had a built in pedometer that could also utilize StreetPass and could've designed it as a standalone app in the same vein as the Dream Radar.
Before I get the whole "anti-Johto" propaganda accusation, I love Gold/Silver and Stadium 2. It's specifically gen 4 and HGSS that I believe are highly overrated. Regardless, they're still very good games.