Kes was my favorite actually, she was hamstrung by the script but Lien was actually a very talented and emotive actress, it's a shame she wasn't given more to do and more time on the show as she had real up-side imo. Wasted talent.
B'Elanna was very good, and evolved a lot over the course of the show.
Janeway, hmmmmmm not the best imo, Mulgrew was OK but in the captain role she didn't stand up to Shatner, Stewart and Brooks.
Seven, I agree with Bry, I found Ryan a downgrade from Lien. Boring character, just pure eye-candy and was teased to be an evolving character but perhaps not given enough time to do it properly. By the end of season 7 she was much the same as she was in mid season 5, and imo that's a failure in character development for a person supposed to be finding their humanity.