Like any of these arguments, the datum matters. All-time, 1970, 1979, 1984, the lifetime of the current players, whatever works best for UConn?
Personally, rules of the time aside, I'd pick the Alcindor UCLA era as the time when people began to care about BB. Every fan knowns those teams and very few know anything before that era. Yes, it's biased in favor of UCLA, but so be it.
The 64+ team bracket is another option, but that excludes the aforementioned UCLA, Bird/Magic, and the bulk of the Bob Knight indiana run. Seems tough to talk history without including those.