Leader Singers, original or new

It seems like everywhere you turn these days bands are replacing their lead singers for new ones, especially in the rock world, of course this is nothing new but in my opinion nothing is as goo das the original vocalist for example, Queensryche without Geoff Tate isn't truly Queensryche, another older example of this is when Rob Halford was replaced in Judas Priest, now I'm not saying that these replacements were bad vocalists it just isn't the same, when I go to a show I want to hear the guy who made me like the song in the first place, of course with that being said I certainly need to throw a couple of examples out that where improvements if not equals and those were of course Iron Maiden when they replaced Paul Dianno with Bruce Dickinson or when Van Halen replaced David Lee Roth with Sammy Hagar (we won't mention Gary Cheron, Yikes!)  it's great that a band wants to carry on and  continue bringing music to the their fans but why not change your name?  When Motley Crue replaced Vince Neil with John Corabi it should not have been called Motley Crue, which I think was one of their best albums they ever made, but you get the point, if Led Zeppelin ever tried to hit the road with a Robert Plant wanna be, OH MY!  I'm sure everyone has their opinion on this and I will attest that I am good friends with some bands that have replaced their lead vocalist and they are making some amazing music but in my opinion it's just not the same, do we really want to hear 18 and Life from anyone other than Sebastian Bach?  What are your opinions?  Let me know!