TL DR version of what Nautilus just said:

 

+ movies/themepark/mobile games, helps sell (the lost) casuals (from DS/Wii) on Mario & Zelda.

+ Third Party seems slightly better than Wii U, and unified Games library means less 3rd party needed to sustain device.

+ Lack of important 3rd party titles needs to be overcome with explosive sales start early in generation, to make Switch seem more attractive to develope for.

+ First year is important, trailer did well. Needs launch titles to repair broken brand trust by Wii U.

+ Wii U failed due to bad 1st year titles.

+ Dena will help them make a better OS, more onpair with the competitions OS's.