The greatest issue I can see regarding notability as it applies to RPGs is one due to IP. There are certainly many aspects and items within RPGs that are notable, and plenty that aren't. However, finding a "reliable secondary source" for many items in RPGs is limited simply because copyrights preclude the use of said aspects in secondary sources.
Consider, for example, Vecna. He has a history, has been involved in many different products, and even has a non-TSR/WotC tale associated with him (The Head of Vecna). I would argue that there are no doubts as to the character's notability. However, virtually every reference to Vecna can be traced either to a published primary source (TSR/WotC), or to a "fansite". Green Ronin, for example, couldn't write about Vecna and publish it. There is little call to discuss Vecna in a newspaper.