I was thinking about the upcoming Avengers vs X-men (not X-men vs Avengers!), and mutant registration. One thought led to another and I was wondering if any mutants or meta-humans exist who aren't super heroes? It doesn't matter if the 'powers' or 'abilities' make them crime fighting potential or not, I'm just wondering if they exist?
I hope I'm reading the question correctly...
To point out the obvious, there are plenty of super villains, which would qualify, but I suspect you're actually looking for meta-humans that are simply living out normal lives, and not getting involved in the struggle.
In that case, there are plenty of examples of super-powered beings that might qualify. It's been years since I read comics, but I remember the Morlocks in the X-Men series living out their lives underground until the Marauders came in and slaughtered a bunch of them.
There have been others that various super teams have run across that seem to want to live out a normal life, but get sucked into one adventure or another, simply because their powers either make them a target, or get them in trouble, or some superhero team simply encounters them, they play a minor role in a storyline, and are rarely seen.
I don't know whether you'd count these as superheroes, given that they only interact with active heroes/teams by chance, yet they often perform heroic (or anti0heroic) acts in these story lines.
Various superheroes also try to leave the hero business and live a normal life, but they invariably seem to get sucked back in for some reason or another. Circumstance and moral character usually combine to provide a situation where their conscience can't let them sit idly by.
I'm sure there are others out there that have never "gotten involved'. The problem with identifying all of them is that if they didn't meet one of the above situations, they wouldn't likely have a reason to be included in the comic at all. Why would the author identify a super-being without reason?
There are a large number of mutants in the Marvel Universe (back when there were a large number of mutants, at least) who's mutations don't do anything but change their physical form (such as being exceptionally hairy) without conveying superhuman abilities.
The majority of these mutants simply try to live a normal life. You'll see them in the background (and sometimes foreground) of x-men comics, especially when they're discussing anti-mutant bigotry or actions.
The Friends of Humanity on the 90s X-men cartoon seemed to love to target these guys. In particular there was one stock background character who's mutation was to be exceptionally hairy (shown by a full beard, somewhat disfigured (hands were unusual looking, fairly ugly by typical standards), etc. He got picked on a lot, but had no special powers.
These characters don't usually feature in the comics, except as victims - lacking useful powers or abilities, they simply lead normal(ish) lives - this does not usually make for interesting stories.
I think it depends partly on how you define fighting crime, and how loosely you're willing to go in terms of "normal". Since you tagged it Marvel, the best I can think of is maybe something like Marshall Law...which was technically Epic, but Epic was/is a Marvel imprint.
If you're willing to look outside of Marvel, and can more clearly define how normal you want their lives to be I can probably do much better.
EDIT: A cursory Google search turned up a Marvel series called Loners - which I'm not familiar with - that might fit with your criteria.
Sentry is a super hero with the power of a Million exploding suns but has to cope with agoraphobia and the fear that he'll lose control of his powers. He eventually overcomes this, but until then he just lives a normal life in his cabin with his dog.