Seton Hall was good for about 5 years in the late 80's-early 90's. They had never even made the NCAA tourney before that, and they've only had the occasional good team since then.
Villanova had some successful basketball history before 1985, and they've been the much stronger program since their title than Seton Hall has since their title game run in 89.
If Seton Hall had pulled it off in 89.....I really don't think things would've turned out much differently for them afterwards. That's going to be a difficult place to win consistently at, regardless.