If you found Ulysses confusing, what would you think of Finnegan's Wake? Ulysses is practically a children's book in comparison. As for the lack of 1984, Orwell was an important author sure, but not particularly a good one. People read 1984 and Animal Farm for the messages, not for the exquisite prose that someone like Joyce can manage.
Sorry, I haven't tried to read that one. If it's even more, hm, abstract?, then I won't ever try.
Note that 1984 is listed, just as "Nineteen Eighty-Four". I missed it when searching, didn't think of searching for "Orwell" instead.
I'd disagree with you about its quality, I remember it fondly (well, as much as possible given the topic of having one's identity erased), it was a powerful experience - and I do remember it vividly, so when asked for books one remembers I'd absolutely mention it, and in a list of books of the century it does belong.
Joyce "prose" on the other hand did nothing for me but make me despise his book.