There were three printed versions of it. 16mm, 35mm, 70mm. Negative format was 65mm. Only for 35mm prints, was it 2:35:1, everything else was 2:20:1. Few theaters were setup for 2:35:1, so everyone saw the 2:20:1 format. When it was restored in 2011, it was done in Digital Cinema 2:20:1 & Panavision.
As has already been stated, Netflix can only send out what they get from the studios on the Master, to either create their rentals, or the mass discs from the studio to distribute as rentals. They cannot just up and create a format to deliver to their customers, unless they get it from the studio in the format customers want.
BTW, the 50th Anniversary edition is in Wide Screen. http://www.amazon.com/West-Side-Story-Anniversary-Blu-ray/dp/B005BDZN62/ref=sr_1_1?s=movies-tv&ie=UTF8&qid=1374905586&sr=1-1&keywords=west+side+story+50th+anniversary+edition
Netflix shows that they rent the Blu-Ray edition.
Joseph, did you double check the unit you are playing back the disc on, to make sure that it is setup properly? What is the make & model# of the player or device you are playing back this movie on?