I'm a fan of Blargg's NTSC filter[a], included in snes9x-gtk.
[a]http://slack.net/~ant/libs/ntsc.html
http://gamasutra.com/blogs/KylePittman/20150420/241442/CRT_S...
http://gamasutra.com/blogs/KylePittman/20150420/241442/CRT_S...