Of the certified and mass produced, Gretzky is #1 and Orr is #2 and Howe was #3 for many years. Maurice Richard is coveted by most serious collectors but not nearly as much as the other three. Of course Cut autos of Tim Horton, Jacques Plante, Pelle Lindbergh, Turk Broda,etc garner big coin.
Patrick Roy, Martin Brodeur, Mark Messier, Joe Sakic, Steve Yzerman, Bobby Hull, Frank Mahovlich, Peter Forsberg, Dave Keon all do well with a larger group.
There are others that are very collectable and sell well despite not being HHOF like Felix Potvin, Marion Gaborik, Mats Sundin, Eric Lindros, etc.
Just my opinion.