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

Assuming it hasn't done so already, Call of Duty.

And Grand Theft Auto will eventually overtake it unless Pokemon Switch manages to be for Pokemon, what Breath of the Wild is for Zelda, and Odyssey is for 3D Mario. A fresh, new, innovative take on the series that now only brings back old fans (like Odyssey did in a way) but also brand new legions of fans (like Breath of the Wild most definitely did).

the only way pokemon can get away from the throat of gra 6 is if they pull a pokemon rby on pokemon switch... or maybe if they release gta 6 after pokemon 8th gen and 4th gen remake... maybe just maybe pokemon will still above gta even after gta 6 XD

Cod will be first to beat pokemon.. Gta will beat it too but it will take 6 or 7 years after gta6 released. That's assuming gta6 can sell 100m in 6 or 7 years just like gta5

CoD

Yearly franchise vs yearly franchise, but CoD being multiplat means it can catch up much quicker

COD and GTA are the only one that can do it - and they WILL do it. Unless Pokemon stops that, somehow.

I'm going to be THAT GUY - Pokemon is not technically yearly : P 

Unless no Pokemon games get released ever, don't even think about it. In fact, the Switch Pokemon will make the gap considerably wider and will continue to sell over a good amount of time.

True but Pokemon has 2 games a year (people on here know that sales would be quite a bit lower if there was only 1 version) and a 7-year headstart. Pokemon also has a lot more spin-offs (it had 4 just in 2015).

But besides CoD and GTA, I think FIFA shouldn’t be too far off. It’s probably over 200M atm.

The thing that will stall its sales is install base. The reason Pokemon has those numbers is because it sold very well on a handheld that also sold astronomically well. Unless Nintendo starts making handhelds again or their hybrids sell like their handhelds use to, it's going to hurt Pokemon's sales comparatively.