Someone suggested in the comments about giving me some indie games to play so I focus on more games here on Nerf NOW!!
Outside writing about popular games being flat out more lucrative; they are linked more because more people play them, making a joke about an unknown game may flop, hard.
When I played Dungeon of the Endless, there was a mechanic which made enemies pop from dark, unpowered rooms. Since the game has cameos from the TF2 mercs I really wanted to make a joke about it. Something about leaving Pyro behind and being slowly surrounded by more and more monsters while blissifully unaware of his inpending doom.
However, people who didn't play the game would not understand why nasty creatures are appearing from dark rooms. I would need to explain the mechanic, and then tell the joke... all of this in 3 or 4 panels. Sometimes this is possible, but usually is not, and in the end I'm still making a joke about a game which less people played. However, if you played the game, the dread of being near a dark room is intense. People relate to it, and this is very important for good jokes, like being on fire and dying near a health pack on TF2.
A popular game is played by more people, making it both easier to write about and more profitable, plus since the game is popular it means more people play the damn thing so they'll relate to the joke more.
If there is an unknown game I like a lot I may make a joke about it, be it because I like the characters, found an amazing joke or just because I want to support it, but doesn't change the fact working with AAA titles is better for the reasons I stated above.