The most successful comeback of all time is Fall Out Boy. They have developed their sound into their own signature pop rock sound. They don't sound like anybody else. They are massive again with a new sound. They write their own songs and have one of the best singers. They are popular again because their songs are good and for no other reason. They always had talent and you could hear that in their old songs. When you have talent anything is possible. Folie A Deux was ahead of it's time and flopped. Now they have continued in that vein and have been successful despite the previous album not doing so well.