The greatest player in the world moniker has always been bestowed upon forwards that were GOAL SCORERS with playmaking abilities. Flip the attributes, look at forwards that were primarily playmakers with some goal scoring and you end up with Bernie Federko, Adam Oates, Niklas Backstrom, etc., all fine players but usually immediately eliminated from greatest player discussion.
The Lemieux-Gretzky debate didn't really heat up until Mario raised his goal scoring pace while Wayne's dropped in the late 80s.
If you take a close look at Crosby's numbers, his goal scoring has been in a steady decline since peaking in 2009-2010. Take all of Crosby's NHL games, playoffs and regular season, starting with yesterday's game, and work back in 82 game blocks:
82gm Block #1 - Includes games from 2009-2010 - 51 goals
82gm Block #2 - a little of 2009-2010, 2010-2011, 2011-2012, a little of 2012-2013 - 47 goals
82gm Block #3 - 2012-2013, 2013-2014 - 39 goals
82gm Block #4 - 2013-2014 & this year - 26 goals
That's a steady decline into Bernie Federko land. The question is whether it will turn around or is this the new 87. If it is then the crown must be relinquished.