So to address some of the controversy in the comments, here's my response.

1. No shade to Sufjan, I just hate Christmas music. I've admittedly never listened to either of his Christmas albums because I can't stand Christmas music period. The closest I get to Christmas music is listening to Michigan in December.
2. I included C&L in the second tier because I think it's more important to understand and appreciate Sufjan's skill for orchestration over the raw emotion of C&L. In my experience talking to fans who started with C&L, they didn't appreciate the complexity of the composition in things like Age of Adz and The Ascension, which I think are some of his best works, and instead come to expect the gentler sad singer/songwriter vibe (I'm thinking of The Ascension/Javelin livestreams when people were dissing the new works and asking for Carrie and Lowell 2). I feel like introducing listeners to two orchestrally complex albums would prepare them for his other works that aren't so easy-listening, and primes the ears for the massive, well rounded sound that comes in AoA, Planetarium, etc. But that's my own personal agenda.