The thing with Wicked is that it will always appeal to a large demographic because of the nature of Elphaba and G(a)linda. As the show gets older, there will always be those teens/YA that see themselves in the two leads, and so I can't see it closing any time soon.
Personally POTO never appealed to me much, but I think when people don't know much about b'way, that's the show they automatically gravitate to. So again, though I think it seems cheesy and overdone, it's still an easy pick for those just wanting to see a show.
Anyways, point being;
1. BOM (I LOVE this show, but you never know with the SJW out there. I'm looking at you, Great Comet)
2. Hamilton
3. POTO
4. Lion King (Though I can see Disney bumping it out should a good moneymaking opportunity shows)
5. Wicked
and of course as others said, if Chicago was on this list, it'd be #1