Fire red will always be my number one as it was my first game.
Otherwise it's a hard choice between Sapphire and Heartgold. Both had great regions and lots to do.
My most played would be Diamond and it was good, but sinnoh was never my favorite region.
I'd blame a lot of this on the destruction of our communal living patterns. We used to live in extended family groups. It was reasonable and expected to live with your parents and siblings. If you did leave the family home it often was just to build a home on the same property.
But then the idea of the nuclear family was popularized, probably to make more money and sell house, and here we are.
To be clear since what I said has been immediately misinterpreted, family centric living patterns were torn apart by capitalism. It heavily favors capitalism when we are separated from each other and lose community. This wasn't a benign social shift