User blog comment:RegularCat/Unknown Songs in the Just Dance 2015 Gamescon trailer!/@comment-2133744-20140813162626

I keep on thinking that the 5th one is Not a Bad Thing by Justin Timberlake, because there's a line in the song that goes, "And if you fall, you'll always land; right in these arms, these arms of mine," and in a brief preview of it, the lead dancer (whose gender I do not know) falls in the arms of each of the backup dancers. Additionally, the background is a golden autumn, something that's smooth and joyful, and I think that could fit the song.

As for the first one, that could be a possibility, but the lead dancer looks to be female, and the group that made the song, Eiffel 65, contain three men. I don't know if Ubisoft would make a trio routine where the lead dancer is the opposite gender of who's (mostly) singing. Although, Ubisoft sure does like to play with our minds. I personally think the first one could be Dark Horse, provided the lead dancer is a woman.