I'm not making it up; if you google the phrase "better Unix than Unix" you'll find a number of references to these words. However, it probably wasn't a direct quote by Bill Gates, as was claimed.

http://www.uniforum.org/publications/ufm/aug96/unix-nt.html

https://books.google.fi/books?id=g0CPF6MEFcUC&pg=PA1&lpg=PA1...