why does every one credit xmen for starting the superhero craze when blade came before and made a boat load of money
Because the X-Men are more popular. I don't think many people (besides hardcore comicbook fans) even knew who Blade was. Let alone that he was a comicbook/Marvel character, to the casual fan it was just another vampire movie.
That and the fact that Blade was R limited the audience significantly, as opposed to the X-Men movies, which were PG-13.