Metroid Prime 4? Shadow of the Colossus? I don't know. For my money, the best thing announced at E3 is the Super Mario Odyssey theme song.
You heard an abbreviated version of it during the Super Mario Odyssey trailer: A big brass band-backed swing vocal performance, a woman belting out earnest lines about jumping and collecting coins and moustaches. During the breaks between its Treehouse Live performances, Nintendo played the full four-minute version with all the verses and the big finish.
The first indication to me that this song was really good was that I was humming it to myself after the trailer. I just want to keep listening to it. The melody is instantly catchy and distinctive. I love the musical phrase on the line "we're the ones who made it this far" (and the vocalist nails it). The lyrics perfectly ride the line of being on-the-nose about the game's action while also feeling like universal sentiments.
It's easy to put a vocal song in your video game, but it's difficult to do one that actually resonates as being good and not unbearably cheesy, awkward or grating. "Eyes On Me" from Final Fantasy 8 is well-liked but the lyrics have some trouble with English syntax. "Snake Eater" from Metal Gear Solid 3 gets into some ill-advised stuff about tree frogs.
Vocal songs tied to Mario games have been around almost since the beginning of Mario games. There was one in 1986 that's appeared on official Nintendo soundtracks, but it was never in a game. There was also a beautiful steel-guitar rendition of "Epona's Song" from Ocarina of Time, with lyrics written by Shigeru Miyamoto himself. But neither of these songs were actually used in games, just soundtrack albums.
In an AMA on Reddit, Super Mario Odyssey producer Yoshiaki Koizumi said that the song is in the game, and it's sung by Pauline, the Donkey Kong damsel-in-distress who is now the mayor of New Donk City in Odyssey.
Thematically, it reminded me of the openings to Disney Afternoon cartoons. Actual Musician Kirk Hamilton says that the Odyssey song immediately reminded him of the Broadway standard "Almost Like Being In Love". An original, up-tempo vocal swing number for a game — I mean, that's ambitious. There are a lot of potential pitfalls. Nintendo took a big chance on creating something that very few video games have, and hit a home run. Now, when's the live concert?