Marvel hasn't had an "official" reboot. However, over the years they updated or changed continuity or story aspects of individual titles to handle the fact that the Marvel Universe has been around since (our time) 1960 or thereabouts.
Some examples include:
- Reed and Ben were originally WWII vets. Now I'm not sure if either of them were ever in the military.
Tony Stark was originally injured in Vietnam. Now, [I think] he was injured in Afghanistan.
Captain America was in the ice waaaay longer than he used to be.
In an early Spiderman story, Peter went on the Ed Sullivan show. Obviously, in current Marvel continuity, that couldn't have happened.
Actually, I thought Tony had been injured in the Korean War.
And let's not forget the story where Cap and Wolverine teamed up in the forties to save a young Black Widow.
