>>51688492Heartgold and Soulsilver if we're talking mainline. There's tons to do and it's all fun. After that is Emerald, because Hoenn is the best region and somehow I never get tired of scraping together a half-decent team for the frontier using gen 3's shit breeding mechanics and limited tms.
I will give a surprising honorable mention to Omega Ruby and Alpha Sapphire for having the best online of any mainline game in the PSS + secret bases. XY had the PSS too but ORAS has them beat everywhere else. If USUM had kept the PSS they'd be here instead, but they didn't.
For spinoffs, I love Blue Rescue Team and Explorers of Sky but rarely do I find myself wanting to start over in them. But their only real competition are the snaps and pinball games, so I might give them the spinoff crown.