Baudolino is basically a story about a medieval storyteller / archliar (either description works, really) who claims to be the Holy Roman Emperor's adopted son, and to have travelled to some of the places that were famous in medieval legend, like the land of the Christian ruler Prester John that was supposed to be somewhere deep in Africa. A lot of the plot features such fantastic characters and creatures - some of them are still familiar to us, others are more specifically medieval. As I was saying to Tom, I enjoyed it, but it's been a long time and I'm not sure if I still would; the unreliable narrator thing is not to everyone's taste, in any case.
Also, out of those four, from what I recall (Name of the Rose I read even longer ago), I'd have to say I probably do prefer each of the other three over Baudolino...
The best part of the book, for me, are the letters between the two Victorian characters, Randolph Henry Ash and Christabel LaMotte - the things said in them, and of course the things not said in them.
It's intentional that the modern people are so awkward and boring (or in the case of Roland's big rival, not boring so much as ludicrous) - but after all the excitement of their radical history-rewriting discoveries about Ash and LaMotte, you could say that they do also become more interesting and balanced people with more exciting lives, thanks to that experience.
You could write whole essays or even books about Possession and its meaning - the relation between the biographer and his subject, the satire of academia, and so on, but I'm not so intellectual a reader that those are the main draws for me. It's the simple gorgeous love story that does it, and the way in which it's revealed piece by piece, with some pieces missing from the puzzle.
I think Byatt has written books that are far more balanced than Possession, with much less awkwardness and rough edges, like The Children's Book or Babel Tower (which is the third and imho best book in a series of four). Better books, arguably, but still I don't feel quite as strongly about them as about Possession.