Well, I'll try my best to help you, since that's what I do around here
A Free Site, in it's most basic form, is a 4 page site that has a warning page, a main page & 2 gallery pages. There are other variations, but I'd bet that 95% of the Free Sites out there follow that set up.
Link Lists list, among other things, Free Sites. Some link lists still list AVS Sites & most list sponsor Pay Sites as well. Some also list galleries, but for the most part, galleries are listed in TGP's.
I think that a good Free Site is one that follows the rules of the a Link List that it is submitted to AND makes sales becase it's listed.
I think that a good Link List is one that's surfer friendly (because we need bookmarkers & word of mouth) and of course, one that makes sales.