Maiden couldn't exsist without Priest (They were the special guest on their shows), and Priest have tried lots of Metal styles, instead of Maiden, that have never desapointed his fans... but are always THE SAME.
I guess I should just ignore your post based on your terrible spelling, pointless arguments, low post count and apparent "noobhood"... But what the heck.
The "this band couldn't exist without that band" argument is so tired. It means nothing, no one can say for certain that it's true and ultimately has no effect on quality whatsoever. Maybe Priest could never exist without Sabbath, maybe Sabbath could never exist without Elvis, and maybe Elvis could never exist without Mozart.
And as for the latter... No. Maiden are hardly less varied than Priest. First, we have their first two albums, punk influenced and clearly different from the rest of their material. The following three albums are the only ones that sound entirely alike to me. On Somewhere In Time and SSOASS, they started to use synths. The change is greater than you'd think if you haven't heard those two.
And then there's No Prayer For The Dying... Simple, down-to-earth. And Fear of the Dark... Certainly an oddity. For better or worse, almost every song on that album is unlike any they've made before.
And The X-Factor. Dark, depressing, and once again they got a vocalist radically different from the previous one. Virtual XI is different in that it's probably the only Maiden album which actually sucks. Their 21st century albums have been a return to their classic sound but with a darker edge, and a greater emphasis on epics.