Loulou's right, Bring it on, Ghost fits the bill perfectly and I found it very entertaining (oh those secondary characters!).
You could check out:
Please Come Back, Mister - amazing and complex plot. There's a bit of romance, but no happily ever after, be warned.
Ms. Temper & Nam Jung Gi - Romance is very light in this drama, it may seem a bit too close to a "slice of life", but the whole plot revolves around keeping their company afloat, it really grabbed me. The first episode may be a bit hard to go through, but it's a really good drama.
Secret Love Affair - there's romance on one hand and on the other bunch of corrupted school heads that drives a part of the plot. The story line is a bit (too) complex, but it's still interesting if you like that...
City Hall - there's a whole political plot going on during the drama, it's overall quite interesting.
I've taken a look at your "plan to watch" list:
Another Miss Oh could fit the bill, romance is still the biggest part of it, but there are a side revenge plot and a little seeing the future plot too. Great drama. (and amazing secondary characters). A must watch!
Lucky Romance - the little bit of plot is only here to serve the romance, making a bad video game about the second male lead, and that's probably one of the worst love "square" I've seen. I was more into it to see the secondary characters couple than the main one... But it looks like most people loved it, so you should probably disregard my comments!
My Lovely Sam Soon - romance, romance, romance. That said the bickering is really funny. I've yet to finish it, but so far it's one of the funniest drama I've watched.
Queen In Hyun's Man - there's somewhat of a plot beside the romance, but really the romance takes a lot of place.
