I think that your original work is actually your best stuff.
By original i mean the stuff that isnt based off any pre-existing characters. And seeing as only the zombie really falls in that catergory i think you know what im talking about.
Your fan art isnt bad, but its not that interesting, it doesnt evoke any new ideas or emotions on the characters, while the zombie shows that you have a sense of humor and a more creative mind than you are allowing yourself to have with the fan art pieces. With those you are simply showing them in the same vein that they have been shown countless times, where as a zombie with a parking cone for a leg is something that i have yet to see, which interests me more than portraying (insert character here) in a (insert typical character pose).
I guess where i am going with this is that formally and subjectively the zombie piece just feels better and garners more interest and a longer look than any of the street fighter characters or wannabe street fighter characters. Because with the fanart you are merely paying homage to a certain aesthetic that may or may not suit you and your style, while the zombie piece allows you to use your creativity unimpeded by the presets provided in recreating a known character.