Illinois and Carrie & Lowell are his two masterpieces in my book. I’d say it depends on if you like the more ambitious side of Sufjan (then it’d be Age of Adz or Planetarium) or the more intimate side of Sufjan (then it’d be C&L or Seven Swans). If you’re looking for something more in between like Illinois, then All Delighted People and Michigan are the ways to go.
:P but yeah, his best album (and that’s saying an immense lot because Illinois, AoA, C&L, 7S, Michigan) even with the redundant inferior second version of ADP in there
I didn’t discover ADP until well after it came out (maybe even after C&L came out) and I was so blown away. It’s not my favorite of his, but I LOVE the balance it strikes between old and new Sufjan.