To replace the dead Ultimate line Marvel should do what DC did with Earth 1 and Earth 2. Make a new universe where the heroes have the same names and similar powers, but their civilian identities, costumes, and personalities are entirely new. In the 616 you'd have Spider-Man Peter Parker, eternal manchild destined to be editorial punching bag, then in the 661166 universe you'd have Patrick Palmer, competent business man who got spider-like powers and successfully uses them to help people while balancing a stable social life.
Weren't the popular guys like Batman and Superman continuous to the point the difference was retroactively applied? Seems that Spider-Man and X-Men would be the same.
