we've never had a definition of gamer, which is why all these stupid threads and articles pop up every now and then in mainstream media when they think they are edgy.
so, *pulls up shirt sleeves*
a gamer is not someone who plays or uses toys. practically everyone does this. out of a number of people who use a game for fun, a smaller number will be a "gamer". it clearly means someone who doesn't .. well .. game .. like the rest of us. The concept is someone who takes games seriously even over the fun.
Now that we have that out of the way, let's completely ignore this asshat definition and look at what "gamer' means today. A gamer is someone whose principal toys are videogames. Videogames are their "this is what i like to do".
It doesn't imply anymore that they take the game seriously, doesn't have any 1337 aspects to it, it's just that kind of person who "i finished GAME yesterday, now i go to store and buy GAME". It's their primary hobby.
Consoles have by far more gamers than PC. You can have PC people who are into eSports but they no longer represent the paradigm of a gamer. Look at most Quake champions and you'll see they never branch out into any other eSport. Well, i mean, there is the Overwatch cash grab now, but these are still people who are fixated on ONE thing and not on games as a broad medium.
As an example, you won't find a chess GM who dedicates himself with the same zeal to a game of Risk.
Mobile gaming doesn't really give a player the option to dedicate themselves to the medium. Games tend to be short, easy to beat, and with dodgy controls. More than games, they fall into the category of "toys".
Console games on the other hand have decently reliable controls and games can be challenging. And console users can pretty much ONLY game on their machine.
PC players can truly dedicate themselves to some eSports due to the superior controls and efficiency of the platform, but are also less likely to spend all their time on games alone, and to have a broader spectrum of media; from my experience, PC users do tend to gravitate towards a genre or another of game.
So, there. Pick your preferred definition of gamer and you have the platform most gamed on. Toys = mobile, Games = console, eSports = PC.
Also, quoting everyone:
PC gamer: "don't call console players GAMERS, they are not true gamers"
Console gamer: "don't call mobile players GAMERS, they are not true gamers"
Mobile gamer: "oh look i can break the pretty candy"