So making over 50 trips to las vegas in the last 4 years. Spanning over several properties and over a million dollars in play-through here are my non scientific casino rankings. (Note I have not visited every locals or downtown casino in vegas.
Rankings are in order of highest slot payback to lowest. I have put locals casinos and strip casinos in two separate sections- Downtown not listed:
New York New York
Off Strip/Local casinos:
Eastside Cannery #1
Green Valley Ranch