Hank McCoy would be stalked by a fanatical group of “furries”
Baron Zemo would have patented “Compound X” (or whatever it was called) and become a millionare. The following year “Compound X” would be pulled from the shelves after several dozen hobbyists found themselves glued permanently to their projects. There would be a slue of lawsuits but by this time Zemo would be living in a palace in Argintina. The Trapster would then become a national hero after discovering a solvant.
90% of all Marvel characters would have died of cancer. (Maybe a bit too RL?)
Batman would go insane from trying to be prepared all the time.
Insane fans would kill themselves trying to pretend they were superheroes.
Fundamentalists would picket Avengers mansion for including Thor on their roster.
A whole new celebrity culture would grow up and surround superpowered beings.
“Simon Williams involved in love triangle. Exclusive pics within .”
Batman would have been shot in one of his first adventures.
Flash would have killed himself by running full tilt into a wall.
Any news about Superman would contain the caption “Don’t try this at home”
Most cities would be wastelands from super powered battles.
There would be dozens of super heroine “nip slip” websites that have JPEGs depicting revealing costume malfunctions.
I once posted that if superheroes were real, we’d have dozens of threads here speculating on the secret identities.
“Okay, Superman is always hanging out with Lois Lane, Perry White, Jimmy Olsen, and everyone at the Daily Planet. Except you never see him and Clark Kent together. Figure it out people.”
Please, people, read ‘Powers’. 
Oh come one, Clark Kent wears glasses and Superman doesn’t. If he was really Clark Kent, he would keep flying into buildings.
And any contacts would just melt when he used his heat vision.
I think it’s pretty obvious that Superman is really Bob Dole. When was the last time you saw the two of them together?
Well, along a slightly different track, Bugs Bunny woulda been shot by Elmer Fudd first chance out, and been rabbit stew.
Don’t forget the SuperCamelToe pages devoted to those tight costumes that don’t cover much.
Comics would be printed in millions of colors, instead of four like now.
Superman’s and Batman’s heads would not grow smaller and smaller each year in comparison to their ever-expanding steroid-fed beefcake torsos.
You would hear actual sound effects, instead of words like SSSSNIK and PKOW and THWOK.
“Graphic novels” would not be quite so unrelentingly gloomy and depressing.
Everyone would exist on at least three or four different lines of continuity, including at least one where you have died, been resurrected, and/or severly disfigured or changed to the opposite gender.
“Nerds’ hard drives, here I come!”
-Black Canary
Supervillains would be portrayed much more sympathetically in comic books. “Doom does not approve of this storyline ! You portray me as losing to that insufferable Reed Richards, when all know that none rivals Doom ! If you not produce a more…accurate…rendition of events, there shall be SEVERE consequences !”
Go dig up the Astro City story, “Where the Action Is.” Available in the Local Heroes collection.
“And what is this ‘closer than sisters’ crap, huh? What are you trying to imply about Sunbird and me?!”
–Nightingale, royally pissed at her comic portrayal
“We can’t run that Doom storyline, Chief! Every comic shop in Latveria will cancel their orders!”
I wonder if, in years to come, we wouldn’t see tragic stories of poorly superannuated superheroes falling on hard times - I am thinking particulalry of Spiderman.
mm
Probably a lot more supervillains would “hang themselves in their cells,” suffer mysterious heart attacks on their way to prison, or just be outright lynched.
It would take about 25 years for the FDA to approve any new drug. (Have to make sure that the new cough syrup doesn’t end up turning people into the Hulk or something.)
MAJOR enlistment bonuses for metahumans joining the military. The Foreign Legion would end up being about 60% superhuman.
The FBI would have a fun time collecting fibers, fingerprints, and DNA samples from super-battles.
All things considered, a lot more supers are just going to end up getting shot in the face.
We actually wouldn’t have organized crime, as we know it, around after the first couple of decades.
We’d have the begginings of an interstellar civilization by now.
The 3rd and 4th worlds would either be a lot better, or a lot worse. (Imagine what happens when the first starving Ethiopian suddenly manifests omega-level telepathy.)
People with invulnerability would go drunk with power a lot more often. (“I’m Superman, I just saved the world for the fifth time this week, and I murder hippies for a hobby. What’re ya gonna do about it? ARREST me?”)
We’d all be in a lot of trouble when “Golden Age” supers start to go senile. (“In our top story tonight, 58 are dead in Berlin after an old man with superhuman strength punched a hole through the Reichstag floor, apparently searching for Adolf Hitler…”)
You’d have to get a “Yankee White” background check to get a job at a museum, chemical supply company, or a toy factory.
And the mini series Love Fights by Andi Watson, which a friend reccomended when I raved about that one.
I still can’t figure out why nobody figured out a guy calling himself The Flamer was gay until he brought it up in issue 11. Sheesh.