Honestly, top 25 albums would probably be a more fitting name, given that I have honourable mentions, and few other categories as well. Some of them are self explanatory, while I want to clarify about the few others.
-Greatest disappointment of the year doesn't necessarily mean the worst album of that year, closer to the point would be that it is an album from which I expected a lot more than I received.
-Biggest surprise is the opposite, it could be either a debut, new band, or just a famous band that put out an unexpectedly great album which exceeded my hopes.
-Hidden gem on the other hand is more like a great album that is (relatively) unknown, or by an unknown band.

P.S. You can also expect that I will redo all my yearly top 10 lists from the previous decade in this format.