I've posed this question before and much the same answers came out then. Since I fist posted this question I've been reflecting on the answer during insomniac nights. I came to the conclusion that Marvel don't have a big three in the same way as DC. DC's trinity represents what the non-fan population know as Super Heroes. Ask someone for another DC character (apart from Superman, Wonder Woman and Batman) and see what you get? The most popular answer I got back, after much deliberating and wrong answers was Robin. Cheats!! However ask people to name marvel characters and you get a plethera of names (some included superman and batman and wonder woman though). Spider-Man normally comes first (ask MJ!! :D ) followed many many different characters - Hulk, Daredevil, Punisher, X-Men - my Dad even rememberd Thor from the Hulk live action special!
Marvel has a stronger character base than DC and this is reflected by what people know as heroes. However DC has two of the three most popular super heroes. Which position would you rather be in?