i personally like the graphics in r/s/e better than any other advance generation game, and as far as gen 4/5/6, ive never seen a hack of those
There are a few hacks of black/white I've seen here and there but due to how the games were made I wouldn't reccomend playing a black/white rom hack without a good computer. I tried playing a plain White ROM on mine and it lagged like hell. It might be the player I used I dunno. I couldn't find any DS emulators other than desmune.