There is the official Angular generator, and many users provided ones for Angular 1. But I haven't found a generator for Angular 2.
Does such a yeoman generator exist already?
There are few generators for Angular2
Please try them and post some feedback or issues in the github
https://www.npmjs.com/package/generator-angular2 (https://github.com/swirlycheetah/generator-angular2)
https://www.npmjs.com/package/generator-gulp-angular2 (https://github.com/x6doooo/generator-gulp-angular2)
https://github.com/joshuacaron/generator-angular2-gulp-webpack
https://www.npmjs.com/package/slush-angular2
(https://github.com/TheVelourFog/slush-angular2)
Generator for creating Angular2 library or plugin
Angular2 Fullstack generator
Ionic2 generator (Gulp; comes in ES6 and TS varieties)