HELP! In Episode 2.20, WIAWSNB, if it's dean's ideal world that he wishes for, why isn't his father alive?

It was not the ideal world for Dean, it was just a world where his mother hadn´t died :)

Dean's wish was that his mother hadn't died. He thought everything in his and Sam's lives would have been normal and "perfect", but as it turned out, he and Sam did not get along at all.