They did make Mario Bros sequels.

Battle mode in SMB 3, coin battle and arguably regular multiplayer in NSMB Wii are both spiritual sequels if not definitive sequels to the original Mario Bros game.

Actually a "real" Mario release consists of an entire game built solely around you playing as Mario in all forms of platforming game mechanics. Games sequels change mechanics all the time but are still regarded as official entries in the series. So by your logic.....Metroid Prime 1, arguably many fans favourite of the series, isn't a "real" entry cause it isn't 2D and therefore shouldn't count? Thats not only obsessively purist but closed minded as well. 

Wait so Super Mario SNES, Mario 64, and both Mario Galaxies don't count in your opinion? Cause MANY.....if not the majority of Nintendo fans count them as REAL, official Mario titles.

You can take comfort in your own little world that is this thread making up your own weird rules but when you exclude Super Mario World and especially Mario 64 you know somethings up lol

....The... lore. I have to admit that part of your argument is the one I assumed you were joking about, but all right.

So let's suppose that Mario Bros.'s setting and characters and elements were propagated throughout the rest of the series, becoming a feeding ground for all or at least the majority of spinoffs (though, uh, this is actually already the case). This would make it the main series?

Fuck the lore. You're trying to say that any game that uses elements of the Mario Universe are Mario games. NO! Hotel Mario isn't a real Mario game. Dr Mario isn't a real Mario game. 3D Mario is NOT, i repeat IS NOT, REAL Mario in the 3rd dimension. Just as checkers/draughts with a 3rd dimension wouldn't be real checkers. 2D checkers would be closer to chess (another 2d game) than 3d checkers.

When you go 3d, you break the game. Space football will break football when players are flying around with jetpacks, it'll be Quidditch. Quidditch and football aren't the same game. Quidditch isn't REAL football. The 2D version of 64 or Galaxy would resemble something more like a mix of Limbo (not a platformer) and Little Big Planet. It isn't checkers anymore even if the pieces are black and white.

I'd like to take this opportunity to apologise for any derailing or trollish or offensive remarks that may have been made in this thread. I take full responsibility and in future I'll ask Khuutra not to contribute to my threads.

Isn't checkers usually black and red

No doubt you Americans decided to change that game too.

You've made kind of a weak analogy. 3D chess is an actual game that's existed for over a century, and it's still tactically similar to 2D Chess, just with another layer of complexity to move possibilities. It's not an entirely different game, and it still uses more or less the same skill set.

Granted I don't know that anyone has ever tried to add another dimension to checkers

Actually, I never mentioned 3D chess and 4D chess is much older that a century.

What I mean is that bringing board games into it kind of illustrates the speciousness of the point, because 3D Chess is very much a real variant of Chess, it's just more complex.

3D Chess might be, just as a 3D racer converted from 2D doesn't have to harm the game and could easily be considered a 'real' or main entry into the series. That doesn't work for all games though. It breaks some games to the point that they can't be considered the same, 'real' game.

Video poker isn't a real Texas Hold em game and Texas holdem isn't 7 card stud.