is in love with someone else at first. The female lead likes the other guy while the male lead suffers. In the end though, she realizes her love for him.

I've seen 9 End 2 Outs which is similar to what I want.

The only thing I can think of is Rays of Sunshine
This sounds like one I'm watching now, except I don't know how it ends... :S

Since his longstanding feelings are not revealed to the viewer initially, it could be considered a spoiler, so--

Spoiler (Highlight to view):  (What's Up Fox?)

@kura2ninja - Can't seem to find it.

@May - Seen it. It was okay. 

@xire - Seen it.
That fool
Bad Love
It's Not That I Can't Marry, But I Don't Want To
I'm Sorry, I Love You
Summer's Desire
You might check out Autumn Tale.  Its got this story line but its complicated because they grew up in same household....I'll leave it at that.  Definitely worth the watch.  It is a heavy flick though, not a light rom-com.  
The Time We Were Not in Love (Taiwan ver: In Time With You)
Bubblegum
Persevere goo hae Ra. Music drama. 
Pretty much the summary of the Time We Were Not in Love.