Dramas where the second lead should have been the main lead?

Any of you guys watched dramas where it was the second lead that got your attention than the main, and deserved a drama centering him/her?

Monstar - Kang Ha Neul drew my attention.

The dramas where I thought the Second Lead was better:

Battle of Changsha
Beethoven Virus
Chicago Typewriter
I Hear Your Voice
Love Rain
Pinocchio
Sassy Go Go
Scholar Who Walks The Night
The Heirs
The Master's Sun
Valid Love

but I've only had Second Lead Syndrome once...can you guess?

Asuko March!
Love in the Moonlight

Warrior Baek Dong Soo - Dong Soo was boring.  Yeo Woon was less so, but the drama itself got so boring that it hardly mattered.  Lost potential all around.
King of Baking, Kim Tak Goo - Yeah, Tak Gu was boring too, and annoyingly plucky on top of that.  Ma Jun was relatable, if angsty.
Time Between Dog and Wolf - second lead was just way more likeable for me. 
Although I'm not sure any of those really needed a drama based on them, haha.  WBDS could have been written from the other perspective, though.

Cheese in the Trap! I don't know if it was because of the contract conflict they had with the Park H, or that I just liked Seo Kang Joon's character more, but that is one of the first dramas that I wish they had filmed an alternate ending.

I almost had SLS for the drama Substitute Princess but because of the overwhelming response of the viewers the story line was actually changed so that the lead ended up with the original second lead. The drama was kind of a mess but it was still interesting.

Does 49Days count too??

Bel Ami
Cheese in the trap

Who Are You: School 2015
The Heirs
Goong
Warrior Baek Dong Soo
Chicago Typewriter
King of Baking, Kim Tak Goo
Pinocchio
Sassy Go Go
She Was Pretty
Sungkyunkwan Scandal
To The Beautiful You
My Lovely Girl
Cheese in the Trap
49 Days (?)
Reply 1988 (?)