They have a very similar feel to them (e.g. dreamy, fantasy aesthetic). Main leads are connected by some kind of "fate", and they are capable of changing the future a little. If you liked Goblin, you might like While You Were Sleeping. Also, both dramas can be a bit slow (Goblin is slower in my opinion.)

Midnight Sun is the original movie version. The "theme" songs in both dramas are also great, and sung by the main actresses. The movie has its own unique charm.