I don't know how people can talk about Kes like she was some epic character. She was trash.
Anyway, Ryan could dance rings around Lien in acting ability.
Ryan was like a more evolved version of Lien in a lot of ways. Much more attractive, intelligent and 10x the actress.
I strongly have to disagree with your statement.
First of all, Kes is definitely not "trash" (none of the Voyager character is) but a highly interesting character who added a lot to the show. Yes, I do find her an epic character.
The point with Kes is that she's both a complement and a contrast to more traditional action characters like Torres and maybe Janeway. Kes doesn't use force unless it's absolutely necessary, she outwits possible problems by moving around it and attacking it from another angle with her wit and smartness.
When it comes to acting, I admit that Ryan is very good but so is Lien too. The sad thing is that Lien wasn't given much opportunity to show her acting skills because Kes was supposed to be more of a background character. When she was given that opportunity in some episodes, she was brilliant. Ryan, on the other hand was given all opportunities to shine since the role of her character was to be the main character of the show.
Personally I find Kes more attractive than Seven. When it comes to intelligence, I'm sure that both actresses are very intelligent.
And even didn't save the show, that is a myth created by those who were in charge of the show. The ratings continued to go down after Seven joined.