> 15 people worked on the OG DOS version of Doom. Many more of course when you start including developers and producers on its ports and localizations.

While Super Meat Boy was mainly made by (AFAIK) two people, the original DOOM was made by an id software that had just 10 employees - this is mentioned in the Doom 3 manual. But this also includes everyone on id, in an article about Quake some months ago Romero mentioned that "We got Doom done mostly with only five people, and then we got a sixth person during the last few months. With Quake, there were only nine of us, but by that time everyone on the team was awesome".

However it isn't just the number of people but also how long it took to make the game. Doom was made in less than a year (or about a year if you include the engine research that went into Shadowcaster) but Super Meat Boy was made in a bit less than two years (and that was with already having Meat Boy as a template).

Heck the original Meat Boy flash game was basically just two or three people. And that alone was enough to get everyone interested.