Sulwhasoo and The History of Whoo are two popular Korean skincare brands. I've used Whoo's whitening range for a few years now with good results but think I'll try something new next. Might give Sulwhasoo's whitening range a go. Tried some samples last month and quite liked it although I'm not sure how good the whitening effects are.
Here is a list of korean skincare brands. I tried a dozen of them and among them I really like IOPE, IASO, O Hui and Dr. Jart+. They are a little bit more expensive but I was a little bit disappointed by the cheapest ones because sometimes their quality is a too low and I couldn't notice any benefits on my skin. I think the packaging of brands like Skinfood and Etude House are well designed but their products are not that effective... For me, they are mostly for younger people than me. I think the most famous korean skincare brands are the cheapest ones but not the best which are more expensive...
I love Innisfree. They have pricey collections but I'm glad that they have middle range as well. They even write on the packaging like which ones go before which product.
Innisfree belongs to low end products because most of their products are cheap and their products are low quality as well.... I tried their products several times and I was disappointed everytime. I agree with the list that Alipark shared with us.
I love SU:M37 and their cleansing stick is holy grail! it's definitely on the pricier range but for me, it's well worth it because I've tried many Korean low end brands and they always seems to make me break out. I'm still interested in trying Innisfree products though they seem like they have great ingredients.
Dr. Jart. Dr. G, Iope, Laneige, Mamonde, Missha, and Mizon are all popular mid-range lines. I lived in Korea for quite a while. When I left, gold hydrogel masks and pig collagen creams were popular. Personally, I want to try the Elizavecca bubble foaming mask.
When it comes to skincare, I think Laneige and Cosrx would be the best one out there. Cosrx is especially known for their acne skincare line and Laneige is mostly known for their hydrating skincare products. Hope that helps!