I haven't built the Steemmonster stats into the system I use yet to collect the blockchain data yet. It's possible but it won't be done until I develop the next version of the collection engine.

However @holger80 has some stats over on beempy: https://beempy.com/steemmonsters
These suggest 4000 Steemmonster players in total over the last two months, which, depending on how those users breakdown into October / November / December users would likely put Steemmonsters somewhere between ranks 2 - 5 on an "author" i.e. user rating.