>>18990429Eccentric Emerald is pretty good, but, it's not really a change everything type of Romhack.
Could try some of the more 'plot' driven ones, but, they're pretty cringe worthy in the story department.
You also could try Pokemon Brown, which is a fantastic Gen 1 hack. There's also the complete 'Fire Red Complete' hack on
romhack.net that only has the first two generations of Pokemon in it though but it's a 'catch em all' hack.
My favorite hack I've ever played is yet another fire red hack, which picks a selection of Pokemon from all generations and puts them self contained in the Kanto region as the original 151. It's not amazingly different or anything, but, it does everything right.
Nuz general has a recommended romhacks list too, which you can find here.
http://pastebin.com/hqfCesbm 
