Ha! I hate opining knowing how much effort and emotion goes into creating a story (just think of someone making a face and saying "Ewwwww!" after tasting your mead) BUT if 4 is worse than 2, which I had to slog through I'm hoping 5 is worth the effort.
I haven't seen any of the TV series, which I understand is redeemed by showing lots and lots of beautiful nudity, which I endorse!
4 and 5 get a bad rap because the characters are split. So any charterers in 4 won't be in 5 and vice versa. So which one you like more will likely depend on which characters are your favorites (but 5 is a way better chunk story by the end of it).
none of them are actually "bad" by any means, however all 5 I feel have issues getting going, but snag you up and don't let go by page 300-400. By book 5 I was just used to it and trudged through the set up, knowing that juicy story was waiting in the back.