I am personally saddened at the replacement of several heroes:
Hulk
Thor
Wolverine
Captain America
and the list goes on and on....
Has there ever been a "replacement" that really worked over the long run (as in 10 or more years)?
The Human Torch (Johnny) is the only one I can think of at the moment (the 2nd one being Wally West if we are talking both Marvel and DC).