>>55500768It is objectively PLA.
PLA has a small side story, a hand full of new sidequests (which are largely nothing), Pokedex completion, Outbreak shiny hunting, and the trials added via DLC.
Every other game has PvP which immediately outdoes PLA as its effectively infinite, and is for many the "real" game of Pokemon in the first place. Even ignoring that huge facet, every other game has a shiny hunting method to match, and Pokedex completion (with far and away more available Pokemon Gen 3 onwards) to match. All other games aside from GS and SV have a battle facility, which alone immediately outdoes everything PLA has. GSC, FRLG, Emerald, DPPt, BW, B2W2, XY, ORAS, BDSP all have postgame areas to explore (ranging anywhere from a single town to an entire region). Different games have various other small or longform features, such as Secret bases, Raids, Contests, etc... that extend beyond post game. SV has postgame exclusive DLC.