[Matrixbeast]

Really? DP was one of the few seasons I could tolerate.
Indigo League: Watchable (Cheesy, but still watchable)
Orange Islands: Depends on how you like Tracy
Johto: Please god let it end. WHY IS IT STILL GOING!? *Cries*
Advanced Generation: If you can survive an episode without wanting to introduce May to the metal end of a shovel, it's still unwatchable.
Battle Frontier (AG Part 2): A step up from the AG. Watchable.
Diamond/Pearl: Watchable. It drags, but it's watchable.
Best Wishes: Fairly decent.
XY: Haven't seen.

The rest are spin-offs, like Pokemon Chronicles and the Ranger special.

Mystery Dungeon: Team Go-Getters out of the Gate (I think there was a second MD spin-off, unrelated to the first, but I'm too lazy to check) and Origins are completely unrelated to the primary anime.