Main series game with the best post-game content?

I loved the Sevii Islands in FRLG. It made the world feel a lot more expansive and each one was just unique and fun to explore.

 

Pokémon Gold/Silver. There was an entire other region added on. For most, it was just a revisit, but for me it was like a brand new region filled with new areas to explore and new secrets to find. I loved seeing how the world changed with the best part being the final battle against red.

Pokémon Explorers of Sky. Not sure how much of this counts as post game, but after you fight the final battle, your only half done with the story and the rest continues through the post game. There's also the legendary recruitment, legendary item gathering, and so much more after the game is done. Not to mention the added extra episodes. This explorers series is brimming with post game content.

 

I personally enjoyed the Looker missions of X/Y. It was actually a better story then the main game content to be honest. The story was interesting and it was cool to get to know Looker a little.

 

HG/SS I guess, if only because it's pretty difficult to top being able to explore an entire region. There were enough changes to make exploring Kanto a second time worthwhile, and with GSC it actually felt like I'd bought two games for the price of one.

That said, I was very fond of Platinum's Battle Frontier. It was a pretty big improvement over Emerald's.

 

Black and White 2 because there is a ton to do post game
- After completing the game you still have quite a bit of the region left to explore,
- the PWT (the battle tree/station/maison/etc.) done right in my book
- the subway (the actual battle tree/station/maison/etc.),
- Pokestar Studios (some scripts kind of being along the lines of puzzles),
- Black Tower/White Tree (fantastic place to level grind),
- Many important trainers you can fight post game (Colress, Cynthia, Cheren/Bianca, N (some of these guys you can fight daily))
- Join Avenue, which was actually fun. I only wish it's S/M counterpart (Festival Plaza) didn't absolutely require you to go there to go online
- And lastly.... Medals (aka acheivements, and something no other main series Pokémon games does)

Edit: Forgot about the Pokémon dress-up contest in Nimbasa city. Not quite contests, but close enough.

 

Gold and silver was by far the best in my opinion. Next was platinum and emrald because of the battle frontier and expanded story. Then finally we have all the gen 6 games because shiny hunting became much easier post game. Sun and moon get an honorable mention with the ultra beast story line as well as FRLG with the sevii islands but in my opinion those things didn't add much to those games. USUM I have yet to finish the post game so I reserve judgement on those games until I finish.

 

Probably SS, lots of things in the post game to do and Red to aim for!

 

BW2
Pokewood (After beating the E4, you unlock more movies), Latias and Latios, Regis, more places to explore, White Forest/Black City with the experienced battles (and a shiny when finishing it) and the shiny Hoxarus for finishing the Pokédex

 

HGSS for sure imo. You get an entire second REGION to explore once Johto is done. How cool is that?!

I also do enjoy the Wormhole hunting of USUM though X3

 

I haven't played all of the games, but of the ones I have played I definitely enjoy the Gold and Silver post games. It's fun being able to explore Kanto all over again, especially with such high level Pokémon.

 

I liked B2W2 post game since the other half of the Unova region was unlocked to explore, white treehollow/black tower, nature preserve, the shiny gible/dratini and haxorus, PWT with the gym leaders from other regions, etc.