Hello! Excuse me but you're wrong... Skyrim like Oblivion is trademarked by Zenimax Media Inc. not by Bethesda Softworks LLC. The only game trademarked by Bethesda is Fallout.
However:
1)Skyrim is registered in the same sections as Morrowind and Oblivion under the class 009 and 041:
Morrowind: http://tarr.uspto.gov/servlet/tarr?regser=serial&entry=76223577
Oblivion: http://tarr.uspto.gov/servlet/tarr?regser=serial&entry=76504923
Skyrim: http://tarr.uspto.gov/servlet/tarr?regser=serial&entry=77017500
2) Most of the MMOs are registered under the class 041, but the description is different:
World of Warcraft: http://tarr.uspto.gov/servlet/tarr?regser=serial&entry=78083850
Dark Age of Camelot: http://tarr.uspto.gov/servlet/tarr?regser=serial&entry=78095779
For Skyrim, it is wrote "Providing online computer games" and for most of the MMOs, it is wrote "interactive online computer games" or "global computer network" .
3) And if we look at the international trademark classification (named "Classification de Nice"), for the class 041, it is wrote "Services de jeu proposés en ligne à partir d'un réseau informatique".
Link: http://www.inpi.fr/fr/marques/boite-a-outils-marque/classification-de-nice.html
So, this class is relative to the online services and a game with this class is not necessarily a MMO.