I question your comparing AM to IM. IM has always been the more popular character and he ranks right up there with Cap and Spidey.
In terms of the general public, not really. Iron Man has never been as popular as Cap or Spider-man until now. I do agree though that IM isn't quite comparable to Ant Man.
Now yes, I will admit, when I first saw the Iron Man commercials, I thought "hmm it could be a Fantastic Four,
or it could be very good." I didn't know if Iron man would be too goofy or not, but I knew that Iron Man had loads of potential for a few reasons.
*For one, a superhero like Iron Man has never really been done before. Robocop is the closest you can compare it to, and even then it's still pretty different. It's new, and it's not the traditional kind of Superhero.
*Let's face it, the general audience love big explosions and guns, which is why they love movies like Transformers and Die Hard. Iron Man has both of these, and it's a Superhero movie, and superhero movies are a popular trend at the moment.
*And finally, Iron Man had a lot of talented actors to back it up.
Ant man has a few things against it right off the bat.
*He's basically unknown to the general public. The average movie-goer has no idea who Ant man is.
*His powers aren't as flashy as Iron Man's. He doesn't have a lot of cool guns or a cool looking techy suit. And their not as unique as a Spider-man character who flips around the city like a gymnast.
Now, Ant Man could turn out to be very good if written well. A good writer can change everything. The Flash is boring as heck when all they have him do is run fast, but when you start exploring ideas like having him vibrate so fast he can phase through a wall, or gain enough momentum that can level a building in a punch, then he becomes more interesting. If the Ant Man writer gets creative with Ant Man's powers then it could end up being very good. But it'll be very tricky.