I think we can all expect male Korean actors to kiss like they mean it, but many female actors, esp those who play in dramas, tend to disappoint in this regard, choosing to either not kiss back or purse their lips.
That's why I agree with everyone who mentions Yoon Eun Hye. I've never seen a drama in which she delivered a bad kiss. She doesn't just stand there and let the male lead do all the work, she actually participates & make the encounter seem more heartfelt and real. Many Korean actresses could learn a thing or two from her about kissing.