I loved him in Fated to Love You, and now I want to see him in more things, problem is I really want to avoid sad endings and plots with no romance. Suggestions?

Thank You..it's a melodrama actually. It's a kind of drama to raise social awareness of HIV/AIDS, but romance is also included :)
I second Thank You, which is arguably one of his best works to date. I'd also recommend Beautiful Mind, if you can get past the first 5 episodes. A Tree with Deep Roots and Chuno are good, but both have sad endings.
I'll look out for Thank You and A Beautiful Mind, not sure I can watch A Tree with Deep Roots or Chuno based on the sad endings... My poor heart can't handle it! I don't mind angst if everything works out well in the end, though.
He was great in the new drama Voice :)

in addition to what others posted:
Shine or go Crazy is one of my fav's
Shine or go Crazy
IRIS 2
Shine or Go Crazy - I agree with that. You like the lead actress but the second lead actress is smart, devious and played really well. I forget the name of the actress but great job by her. I also think the role of the aloof prince suits Jang Hyuk's acting style/traits fairly well.
well that's hard coz many of his great performance was a heart stopper.. So I will recommend BEAUTIFUL MIND.... you will love this one.. :)