What is the WORST mainline Pokémon game?

Worst game is honestly subjective. I mean if we really hold any game to a certain standard then the Gen 1 games in Red/Blue/Yellow obviously qualify because the Type chart is a chaotic mess. Ghost doesn't counter Psychic, ditto Bug because both of their STAB movepools are horrible. Night Shade is fixed damage while Lick is weak and is Physical while Bug has just Leech Life, Twin Needle and Pin Missile, the latter two only appearing on one BUG type that happens to be vulnerable to the very thing its meant to counter. Dragon Rage is it for Dragon STAB(and its fixed damage so… STAB = meaningless) and Fighting has really poor movepools as well(with really awful Special stats that make them food for anything that does Special attacks(especially Psychic)). Pokémon that you'd think would learn certain moves(aka Fly HM) cannot(looking at you Dragonite and Charizard in Red/Blue). Stone Evolutions require training their base forms to a specific level, else lose out on their moves since the evolved forms don't learn anything outside of TM's or HM's. Meaning if you wanted Arcanine to have Flamethrower, you'd have to train Growlithe to level 50. Item storage system is smaller, TM's are one-use and they're gone(cannot obtain more of them) and the female protagonist trainer is non-existent(she didn't even exist until Crystal w/ Kris despite promotional art showing "Blue"(aka Green to USA players) on the box art). Critical Hits are mostly based on Speed… Dire Hit/Focus Energy result in lower Crit chance(not higher) and the AI is frankly dumb as rocks.

S\V gets 3rd in my book

shure the grass sometimes looked like flowting dots but it was fun to play

FEUCOCO

I think Cyrus had good motivations, but they didn't execute the idea good enough so it just felt boring. Platinum did it much better.