I just watched Love Forecast and thought it was amazing is there any drama similar it? , any drama that has the following aspects:

-Friends or guy / girl who was initially friend zoned that eventually date. 

-Romance

-Happy ending

Definitely Operation Proposal (korean version) or Proposal Daisakusen (japanese version) : They are about a man assisting his best friend wedding without ever telling her he loved her. Then he gets the chance to go back in time several times to change the past.

You can also try Reply 1997. I didn't watch it so I can't tell if it's worth watching but that's the theme you're looking for.
Just watched both operation proposal both were AMAZING! Any others people can recommend? 
*Jogs memory*  Hmmm maybe 'In Time With You', '9 End 2 Outs' on the more melodrama side 'Summer's Desire', 'Pinochio'