There are the four wikis you mentioned, and there are some others that have at least been talked about: Ace Attorney Wiki, Glitch Wiki, Gamehiker, WikiFang, Chibi-Robo, Game & Watch, Golden Sun, and Fantendo.
I - with the help of Axiomist and Turtwig A - am also working on Palutenapedia.
Plus, there could be wikis for Punch-Out!!, Custom Robo, Legendary Starfy, Professor Layton, Trauma Center, Art Style, and ExciteBike/Truck/Bots. That gets the count up to 32.
Don't forget the potential fanon wikis, either. Even one fanon wiki for each major franchise (Pokemon, Metroid, Zelda, Animal Crossing, Kirby, and Star Fox) could move the count up to 38.
I would rule out neither a retro wiki (Ice Climbers, Balloon Fight, Clu Clu Land) nor a casual wiki (Wii Sports, Brain Age, Cooking Mama). This brings the total to 40...