Of the three initial “Holy trinity” of SNES games, probably Tales of Phantasia is better played on the PlayStation. It runs just as well, and has much better skit management! Playstation in general runs REALLY well on the Gameshell.
Not a hack, but rather a massive culmination of all of the pokemon games (up to the DS) rolled up into one epic adventure. It’s not quite ready for prime time yet on the gameshell due to the resolution constraints of the device, but nonetheless, this is one of the larger scale hacks that does exist.
Of course, this is also implying that Pokemon Black and White on the Nintendo DS can also be played. Quite possibly one of the best story driven pokemon game out of all of them.
(Also, don’t forget Heart Gold/Soul Silver, and Diamond/Pearl/Platinum were also DS releases)
Another little known Pokemon game on the DS was Pokemon Conquest. Think a cross between fire emblem and Pokemon. It was genuinely a fantastic game that I’m surprised never saw any further games in the series.