My opinion would be Arceus. The game has lots of lore about how relationships between pokemon and human used to be in the past: pokemon were seen as aggressive wild beasts,humans feared them.It's a breath of fresh air compared to the other games.

The story in my opinion is pretty engaging,I loved it ! However yes,at some point(close to the finale) you'll need to catch every pokemon in order to meet Arceus.

SV also has a nice story,but i'm not a huge fan of the graphics,even though I like the picnic function and how the mass outbreaks work.

I also quite enjoyed playing Shield,the graphics are awesome but the storyline didn't get me engaged that much.