Yeah, I find this an odd final 2.
I expected to see CoS there, but was glad to see RotFM
In terms of the actual campaign adventures, I think there are very few people in this thread who really think Icewind Dale: Rime of the Frostmaiden is the best one or even their favorite.
IMO, CoS is the best of the 5e adventures, but it suffers by comparison with the original Ravenloft. However, I was hugely impressed with RotFM, and am looking forward to running it. So I'd probably place that at #2 in terms of quality (of the ones I have), and would say it probably is my favourite.
(I should note that I skipped both the compilation volumes, so can't comment on those, except to say that I do know that some of the originals are great.)