The fight between Superman and Doomsday in DC Comics is a classic. It's a battle of titanic strength. Doomsday is a nearly indestructible foe, and Superman has to push himself to his limits. The destruction that occurs during the fight is on a huge scale, and the fact that Superman sacrifices himself in the end makes it an iconic fight in the world of fiction.
I don't think so. There haven't been any official announcements or indications that the HxH manga will continue. But you never know, maybe there'll be a surprise in the future.