You see where Flash is now? That's about where the big three were before the movies.
They had starred in animated series but not animated series that broke out into the public consciousness the way X-Men or something like TMNT did. They were on T-shirts and lunchboxes but generally in the context of "here's Spider-Man and 15 other Marvel characters on a T-shirt", not "here's a Thor T-shirt" (I say "generally", so please don't link to a pic of this one Thor T-shirt from the 90's you know of
I betcha more people could have told you who Jubilee was than Iron Man before 2007 (I say 2007 and not 2008 because that's when the movie's marketing machine started ramping up). These were not mainstream characters.