I haven't modded in years but I remember a client for halo 2 called dothalo that used to be one of the most famous back in the "olden days". No one probably even knows what it is but brings back many memories. Unleash X and Evox would popular soft modding homebrews for the original xbox. Good more current emulators you should check out are Retroarch and Bleemsync if your into modding ps1. They're really popular emulators. Retroarch is one of the best. I don't use them myself but they are very popular.