Do you mean all supervillains or do you mean all villains, period?
If all villains were gone, 100%, I think you'd get the following:
1) Some heroes would just go back to their natural lives.
2) Some heroes would use their powers for science and such, like how Superman's been seen before disarming nuclear weapons and whatnot.
3) Some heroes would possibly go insane from boredom and turn into villains, but then of course they'd be totally outnumbered and be downed in a few minutes lol. That, or they'd feel bad about themselves for not being of any use anymore, and kill themselves.
If normal common thugs were still around, the heroes would busy themselves with them.
They would be registered by their respective governments and forced into their military or security services.
A few would go willingly, some would refuse of course and go into hiding forcing the registered heroes to hunt them down as criminals/terrorists.
The rebel heroes would eventually get organised and structured enough to fight back.
No doubt the public would be split down the middle with some thinking of the civil liberties and personal freedoms the heroes are being forced to give up because of what they are (either by birth, accident or design)
Whereas others would not want such powerful beings to be allowed to walk freely through the streets knowing that all it would take would be the wrong powered being to have a bad day, get angry... and BAMM.... he knocks over a building and kills dozens of people (or blows up a school)
This situation would continue to escalate with more heroes joining each side every day... some would be completely torn and forced to just leave
It would all just turn into one massive super-powered..... what's the term...civil fight? ... civil battle??? ...... oh yeah.... it would all just turn into one massive super-powered Face Smash Fest!
That's pretty good .....I should sell the idea to DC or something......