I'm a composer currently studying in the Jacobs School of Music in Indiana University. Jacobs is notorious for having the most intensive musical analysis courses in the nation. I've also studied in Paris in the European American Music Alliance, which is Nadia Boulanger's program that has been continued on by her and Messiaen's students.
That being said, I have extensibly studied both Mozart's and Kanye's work extensively. Having done this, I would like to express that I believe that Mozart is one of the most overrated human beings in history, having been mythologized like so many composers of the German tradition of western art music. His work is an exercise in wit and framed emotion, as is so much of the mid-classical era. The theorists of the world salivate at his use of thematic counterpoint in the finale of the Jupiter Symphony and his ability to pivot to new key eras, but he was still trapped in the conventional sonata form, like a virtuoso painter who only has access to charcoal and paper. Indeed, Mozart's actual musical identity is simply a wittier Haydn with less jokes and more gimmicks.
Kanye West has changed the face of modern music. Before he was signed to a record label, he would create five instrumentals a day, every day. He pioneered the manipulation of vinyl speeds to pitch shift samples. This allowed the rapper to be the dominant force in the middle register, while the sample provided a countermotif in the high register. He pioneered the use of lyrics in a sample to hocket with a rapper's lyrics, allowing for a thematic reapplication of the sampled song's original intent to create darker, ironic imagery. More recently, he has completely revolutionized the use of form in hip-hop, using samples in different contexts throughout his albums for thematic development, shifting key areas, and even changing tempos and meter within a song. He has elevated hip-hop in a way that baroque elevated art music the the 16th and 17th centuries.
Therefore, I wouldn't consider Kanye West an American Mozart- Mozart represents refinement and a return to reason. I would call him the American Bach, taking previously established conventions and forms and taking them to extremes for the sake of musical identity and expressionism.
Regardless of musicality, I would take a living artist over a marble bust in a museum any day of the week.