Would there be much interest for a hacked smb or dh? 

A hacked smb would be a custom title screen, custom text on the beaten castle screens, and a 2 sprite changes (like the princess and maybe the put a message in the clouds or something).  That would probably cost $25 shipped.

A larger hack could be done, but the time and effort would raise the price.  I've seen many grandiose plans ending after the second level, so I think that something simple that still would impress is kinda cool!  Of course, you can do the hacking yourself and make it as complicated as you want.

It could just be personalized ala "super *yourname* game", or maybe a theme for a gift "super *theirname*'s brithday"  (like cake for mushrooms and a candle for flowers?). 

Duck hunt could also be fun because the big change would be what you shoot at.  I'm not a crass person, but DH is just asking for a one letter title change and shooting some flying phallus fun...

Sounds cool man I will pm you sometime to do something for me thanks