Hi,
First, allow me to throw my list site,
ePorn List | Quality adult TGP porn directory links and more in the mix, don't know if I'd call it the "best" but I think it does okay. I just put up some new ads that I'm not fond of, so, bear with me on that. Changing them soon.
Anyway, to answer the initial question, I would say it really does depend on what you're definition of "best" is. Try searching google/bing for lists sites, using various keywords, she what ranks on the first page for all for all of those searches and then target them and email them all.
Now, with that being said, if you're looking for solid traffic, then yeah, target those high ranking ones but if you're really trying to build a solid link profile then keep in mind that links from low traffic sites, high traffic and everything in between looks "more natural" in the eyes of the search engines.
Finally, of course some of the above is null and void if the said list is signing up to your affiliate program in regard to link building.
Alright, my two cents