Sinnoh Sinnoh Sinnoh, 1000x Sinnoh! Sinnoh's the best region overall, there's so much great stuff there :D It has all the best Pokémon, interesting places to explore like Mt Coronet and the snowy mountains, the lakes are very interesting, the whole map is completely varied with almost every route, and it really just feels like home playing in Sinnoh. There's so much interesting stuff to do and unique features in Sinnoh that it's a really wonderful region and I've played it countless times ♥
Er...right back to topic. After the world's longest thinking I've decided on the calm,cool Sinnoh. Not just to the fact it was technically my first region but the scenery is great. Windworks to power the region, factories, old untouched caves, more shops it just seemed more like a better region.
The music was pretty amazing too - Cynthia's theme,Cyrus's, your rival's. And I liked the characters better in Sinnoh honestly. Sinnoh also introduced some of the most badass and awesome Pokemon ever. Honchkrow,Togekiss,the cute but powerful Pachirisu and many more :3.
But don't get me wrong, Johto is awesome and all but I'd say my heart lies with Sinnoh.
Layout: Sinnoh > Johto
Sinnoh has a more explorative layout, and its unique settings make for interesting adventures. Johto's is too straightforward, and most of the routes are too short and uneventful.
Atmosphere: Johto > Sinnoh
Like has been said, Johto has a consistent atmosphere and a very natural feel, and the game progression makes sense. Sinnoh has a bunch of things tacked together at points and is a really diverse region to the point that you sometimes question if you're in the same area.
Dungeons: Johto > Sinnoh
If only because Rocket Hideout (in Mahogany) >>> Galactic HQ and Goldenrod >>> Mt. Coronet. Mt. Coronet is awful solely because of the high encounter rate that still spawns frequently even with a Repel. Most of Sinnoh's dungeons were too short, while Johto had two long ones and the Ruins of Alph to anchor it.
Cities: Johto > Sinnoh
There's more to do in Johto. Radio Tower, the Kimono Girls, Olivine Lighthouse, and a lot of interesting places that are in cities.
Gym Leaders: Johto >>>>> Sinnoh
Really now. Johto has some boring folks, but it also has Whitney, whose Miltank gave us all problems when we were kids, the aggressive badass Chuck, the sweet, innocent, yet shy girl-next-door in Jasmine, and the really temperamental Clair. Sinnoh's Gym Leaders, for the most part, were completely devoid of interesting personalities; Fantina was easily the most memorable, although she is French, and Crasher Wake had good design. Overall, though, the rest of them paled in comparison to the titans Johto offered us.
Enemies: Johto > Sinnoh
Team Rocket is the same in all of the games in Johto, and they got it right the first time. In D/P, the random Galacticas have no clue what's going on and that's hilarious, but by the time you've beaten them all, you still wonder that too. It was seriously that boring. Platinum fixed this and added a more intriguing plot, but it was not enough to make it better than Johto. It may be nostalgia for me, too, though.
Additional characters: Sinnoh > Johto
Johto doesn't have Looker. Johto has Silver and Lance. That's it. Sinnoh has Looker, Cynthia, a guest appearance by Jasmine, Barry (who is no Silver but is a decent rival), and the stat trainers.
Pokemon: Johto = Sinnoh
There were some really good Pokemon in both, and some really bad Pokemon in both. Both introduced a few too many pre-evolutions, and that was not necessary in the slightest. Both also had some really great things to offer team-wise, so in the end it's way too close to call.
In the end... Johto! Sinnoh is still great, and nostalgia may have something to do with my decision. I just feel that Johto really set the bar high.
I absolutely prefer Sinnoh. I love all the fourth generation Pokemon, especially the anime. Dawn is my second favorite character, next to Homika. Plus, Sinnoh has that charm that made me like Pokemon in the first place. When Ash was still in Kanto, Johto and Hoenn, I didn't even know who Pikachu was. Well, I think I've made my point.