Galar's main story is easily in Top 3 along with Unova and Alola, and maybe Sinnoh.
Let's be honest, Red and Blue didn't have a proper story at all in its original and remakes except Pokémon mafias who were just another Poison-type trainer in different routes.
Gold and Silver's attempt to revive Team Rocket and reach Giovanni ultimately felt short. HGSS at least made Giovanni available in event and his relation with Silver.
Ruby and Sapphire was all about power freaks who wanted to control nature and outclass one another without thinking no living being can exist without water or land.
Diamond and Pearl displayed good effort with Cyrus' puppets doing all the work for him to create his perfect world. If it wasn't for Platinum, it'd fell short after Mt. Coronet.
Black and White is considered to be objectively the best story.
XY explained the story of Mega Evolution fine, but Team Flare were just ruckuses. The story implying everyone has to die if they aren't perfect and people believing it for 5M Poké Dollars was plain stupid. No legendaries were involved except being revived from tree/coconut forms and a sequel was at least necessary to give its story a justice.
Sun Moon, also, did a wonderful job with an abusive mother going crazy due to an alien's neurotoxin to find his lost husband and work with Team Skull to negotiate her plans.
Galar's main story was Gym Challenge, it was executed perfectly. The Darkest Day needed research as neither Zacian nor Zamazenta was even known in Galar as it was implied both IG and dex entries. The real villain was Eternatus and its episode was well done. Rose's intentions is as same as the others except Ghetsis and Lusamine; is selfish but makes zero sense to take action. Still, battling Eternamax form along with Zacian and Zamazenta, the entire Gym Challenge, character developments for Sonia, Hop, Bede and Marnie easily put SWSH above any other mainline series and just behind Unova and Alola. Maybe if we have a third version, it can focus its lacking parts just like DP and Platinum.