(and its not very often you'll hear me say that! LOL) I don't think his taking a succession of wives in an attempt to secure a male heir was entirely a matter of feeding his 'monstrous ego'. You have to remember that his father, Henry VII's, right to the throne hadn't actually been all that strong after the end of the Wars of the Roses - he had married Elizabeth of York to strengthen his claim. No doubt Henry was raised with a sense of how important it was to secure a strong succession to the throne (and hence stability to his country) - it was not just desirable, it was his duty as king.

Female heirs weren't as desirable as male ones to a new dynasty on several counts. Firstly, there was a poor predecent - the last woman on England's throne had been Matilda, daughter of Henry I, who ruled for a brief, constantly disputed period in 1141. She never titled herself 'queen' and was unpopular with the English people.

More importantly, having a female heir meant the the risk of England ending up in the hands of some foreign power through marriage. A husband acting only as a consort to his queenly wife (as Prince Albert did for Queen Victoria) would have been an unthinkable concept at the time. As it turned out both Mary and Elizabeth would indeed learn the drawbacks of taking foreign husbands.

So although Henry's ego probably WAS as big as his appetite for women, I think he may have had a political as well as personal reason for wanting male heirs so strongly.