Whats the most comprehensive Pokemon game to emulate? Like which one has the most content and the largest pokedex? Or are there any good ROM hacks for like, Ruby, Emerald or Platinum that add more content?
I'm actually replaying the 2 pokemon games people always mention when talking about content, HGSS and B2W2 (I'm on a absolute pokemon streak rn)
HGSS does have a lot of side content and the second region, however Kanto is pretty empty in both the og and remake Johto games. Kanto in HGSS is a pretty good upgrade though, for example, they did re-added a few locations that wasn't in og GSC due to storage space restraints like Viridian forest. Content wise HGSS is also better with more legionaries, swarm and hoenn and sinnoh sound pokemon, and especailly gym leader and elite four rematches (the former also makes leveling up MUCH easier in the late game). One thing that HGSS did amazing is the safari zone, which gives the mid game A LOT more viriaty pokemon selection wise (for example, I used larvitar from the safari zone in my playthrough) and the safari zone system in the post game of switching out biomes and placing down items to find certain pokemon is kinda confusing but also fun imo. I do think HGSS is a bit overrated in how much content it really has given how fast you can breeze through Kanto, but overall still a great game.
B2W2's Unova region is basically doubled in size from BW1. You get to both explore new areas and old areas both in the main and post games, and despite technically being smaller, post game unova in B2W2 has much more content overall the HGSS Kanto. The pokedex has around 300 pokemon, more than HGSS' combined Kanto and Johto dex + some cross gen evos. Also, because of Unova introducing around 150 or so pokemon, it's a perfect split between old and new. There's also A LOT of side content too, pokestar studios, the pokemon world tournament which in the post game allows you to fight EVERY gym leader up to gen 5 including even unovan gym leaders exclusive to the first game. More legenaries as well to catch and they're all in either post game or new areas, and not some dark void like they are found in more recent pokemon games. The graphics are also great despite the game being over a decade old, the game also focuses on the story, but still isn't nearly as dialogue or tutorial heavy as the modern games.
Between the 2, HGSS IS a great game, but B2W2 is just better in everyway imo. I know this is the common answer, but people prop up B2W2 for a reason.
Also DS emulation is way less "solved" than GBA emulating is, but drayano's hacks are pretty great. I haven't played it yet, but I've heard great things about Blaze Black 2 and Volt White 2 Redux.