A rivalry takes two to tango. We aren't rivals with Kansas in anything. The "rivalry" with Nebraska in football was also a Cyclone fan only "rivalry."
ISU/KU basketball and ISU/NU football is apples to oranges, IMO.
We're much closer to having KU as a basketball rival. Go read their message boards. They HATE coming to Hilton. They constantly rip our fans for booing. They refer to Ames as the "Land of 'Boo'". They don't like us. They consider us beneath them, as they should, but we're solidly on their radar. We have more wins in Phog than anyone else. We're second to them in Big 12 conference titles. After Phog Allen, Hilton would almost unanimously be considered the toughest arena in the conference.
Nebraska barely knew ISU existed and couldn't muster much feeling either way.
I wouldn't call ISU/KU basketball a real rivalry, but its far closer than ISU/NU football ever was.