So I recently started a thread called "Love Interests - Who does everyone 'belong with?,'" but I'm beginning to realize that my main goal was really to get some clarity on this topic. I enjoy finding out about those significant figures in a character's past, but I also like finding out about those characters who were deemed "the" love interest at a time. For instance, Superman was introduced in 1938, with Lois Lane as "the" love interest. And that basically didn't change for over seventy years. With other heroes, I'm fascinated by who the different writers have brought along over the years. So I've been doing some research, hopefully people can offer some clarity on any and all Marvel heroes.
I'll start with...
Iron Man
This site is a big help, but it lists just about everyone Tony’s ever slept with, while I’m focused on more major love-interests, and possibly also fellow superheroes who he’s had to continue to interact with.
https://www.republiquelibre.org/cousture/bd/IRNMN5B.HTM
When first introduced in 1963, his main love interest was Pepper Potts, with whom he faced a love triangle with Happy Hogan. She ended up eloping with Hogan in 1967.
At one point, he fell for Whitney Frost, AKA Madame Masque, who later became a supervillain and has been troubling him ever since.
Janice Cord was the main love interest for about two years and twenty issues, from 1968 to 1970, until she was killed. Marianne Rodgers was introduced in 1971 as a main love interest, before she went crazy.
Bethany Cabe was introduced in 1978, and was Stark’s main love interest until 1981, when she realized her deceased husband was actually alive.Tony got together briefly with the Wasp in 1982, until he revealed his true identity to her, and she became disgusted that she’d been involved with one of her ex-husband’s best friends.
Tony also had a brief thing with Heather Glenn before she killed herself, and, based on that site, also fell for characters named Veronica Benning, Rumiko Fujikawa, though I’m not sure if these were very extended romances.
Stark got back together with a now-really-widowed Cabe around 1995, but when a new volume of Iron Man started, this was apparently just forgotten about.
Happy Hogan died in 2007. After the popularity of Pepper Potts in the movies, she again became a central love interest in the comics, the two hooking up in 2009., but circumstances soon cause Tony to forget that ever happened. There was also an incident where Cabe came back in the comics, and she and Pepper did not get along, probably due to their mutual involvement with Tony. Since then, she’s been engaged briefly, but I really don’t know what’s going on with the two of them now.
So it seems like Pepper and Bethany are the only two characters, from what I can tell, to be persistently present love-interests in the comics.
What drives me crazy is that I cannot find anything online about Tony's relationship with the Black Widow. You'll notice that the above sight only lists her insofar as he had an attraction to her in her first appearance, before she turned out to be a Russian spy. Now, I've been pretty sure for a while now that the two were rather seriously involved in, I think, the '90s, but google-search as I might, I can't find anything about that!
He also had a lingering mutual attraction to Maria Hill, which culminated in the two knocking boots at one point, though I don't think it led to anything but awkward-zone after that.