I remember when Nico Nico Douga medleys were an annual thing and although that a few would come out every year, there was always one that was indisputably the "medley of the year" (e.g. Kumikyoku, Ryuuseigun, Nanairo). But since 2011, it's gotten a lot harder figuring out which one's the best.
Ok this is my favorite melody off all time! (Next to Nico Tale of course but this is a very close second) the only reason why Nico tale is still my favorite is because they included the Ending Theme song for my all time favorite anime Axis Powers Hetalia.