Creighton was established before Altman, they had a lot of success under McManus, Eddie Sutton, and Tony Barone (multiple Sweet 16 appearances, and that was back when only 25 teams made the tournament). They went through a tough stretch in the early and mid 90s at a time when Nee had success at Nebraska. But overall, they have always been a much more successful program than Nebraska. Nebraska has never had any sustained success, just a few decent seasons overall mixed in with many mediocre to awful seasons.
Creighton may have had more success way back when, but for a 20+ year stretch between '78-'98 here is the comparison:
NU: 7 20-win seasons, 5 NCAA tournament appearances, 0 NCAA tournament wins
CU: 5 20 win seasons, 3 NCAA tournament appearances, 1 NCAA tournament wins
Head to head record: NU 16 wins, CU 6 wins
Point being, for 2+ decades, Creighton was no better than NU and arguably worse. The kids Altman and McDermott recruited to help build Creighton into the program they are today likely cared as much about what success CU had under McManus and Sutton as kids Matt Rhule is recruiting today care about NU's under Bob Devaney.