Not talking about the crossover series and such. Certainly not a sanctioned projected. It was based on the idea that an alien race had come to Earth and killed almost all heroes and(I think) villains of both universes. They were actually combined in the same universe from the outset. The basic plot had the next generation taking up their place. I remember Thor was replaced by the Sigurd Jarlson version and a Superboy or Superman along with many other 2nd generation characters. Not much else in the memory department. I say yes there was some such while others think I have reached early senility.