Who's the richest Superhero?

Forbes Magazine actually did a list of fictional characters with the most money... this is the magazine that also ranks the real richest in the world. Lex Luthor and Bruce Wayne both were in the top ten, no Marvel character was.

Namor is pretty rich.

I presume, that the Atlanteans (especially Namor with his ability to communicate with the sea life) know about nearly every sunken ship. Antique objects have a geat value. Professional treasure seekers pay millions for diving equipment, because it's a profitable market.
I'm sure, with his possibilities and knowledge the Sub-Mariner could collect millions as easy as land dwellers pick flowers.

On the other side, even as we know he's a capable business man and perhaps he could be world's richest man, money and wealth doesn't mean much to him. This is a land dweller's thing.
Let's say it like this: If he wanted to, the Sub-Mariner could buy everything he desires.

This is from National Geographics:
"Underwater explorers may have hit the mother lode with the discovery of theCivil-War era S.S. Republic. The paddlewheel steamship went to the bottom of the Atlantic in 1865 with a cargo of gold coins that may be worth as much as U.S. 180 million dollars."

Namor
Aquaman
Black Panther
Lex Luthor
Bruce Wayne
Green Arrow
Dr. Doom
Iron Man
Professor X

lets put it this way, everyone who rules a nation is # 1(except for Reed who at his best was richer than everybody put together), everyone who runs a multi billion dollar corp is #2,(though some are obviously wealthier than others)everyone who is of serious royal ancestry is #3, everyone who inherited a fortune is #4, everybody else is irrelevant