Honestly, MSG is the MOST accesible of the romantic comedies, with probably Sex is Zero close behind it. If you're really interested, check out Singles (yes there's some romance, but it's not typical guy and girl get together kinda thing) and probably My Tutor Friend, which followed the year after MSG and was a pretty big hit. MTF though has a lot of cultural Korean references that may not be picked up on, but it's still okay. Arahan is a weird hybrid; think the comedy of Shaolin Soccer meets Spider-man, (with a brief touch of romance thrown in for good measure) and you're pretty close.
Others include: Someone Special, Crazy First Love, Oh Happy Day, Windstruck, Wet Dreams (Wet Dreams 2 just came out in Korea) and My Little Bride. They start becoming pretty typical though after a while, and it seems that the K industry just keeps churning them out at an insane rate.
On the other hand, Koreans know melodrama like no other. Seriously. If you want some more romantic, less comedic, more melodramatic films, check out Failan and Christmas in August for sure. Also good are The Classic, Bungee Jumping of their own accord, and One Fine Spring Day.