https://en.wikipedia.org/wiki/List_of_best-selling_video_game_franchises
NOTE: I will based it on these numbers
pokemon franchise is sitting below Mario with around 300 million
Pokemon will likely be overthrown to it's second place soon or in the near future... but who would overthrow it first?
here are some franchises that will most likely over throw it...
Call of Duty - around 275 million... strong annual sales that will definitely de-thrown pokemon if they keep selling more than 10 million a year...
Grand Theft Auto - sold more than 70 million on their last game... even if they don't make games as fast as COD, Pokemon or FIFA but heck their sales sky-rocket every entry.
FIFA - 100 million... even if it is far from pokemon sales... this franchise have been selling more than 10 million copies a year for some years now.... and football don't die!
Sims - 200 million... this game just won't die!
Minecraft - 144 million... i dont know how they count this but probably outsold pokemon already :P
Dark Horses:
Need for Speed
Lego
Final Fantasy
NFL
Pretty Much Dead:
Tetris
Wii Series