This was the first Hip Hop album. Kurtis Blow, Grandmaster Flash & The Furious 5, Sugarhill Gang, and Sequence had albums before the Wildstyle Soundtrack but they weren't all rap, they had R&B songs and ballads.
The Wildstyle Soundtrack was the first Rap/Hip Hop album that was THE REAL THING.
Also, it was the first official record with scratching. (there were a few earlier albums called Live Convention 81, and Live Convention 82, but they weren't really albums, they were just recordings of live shows in a compilation that the artists had nothing to do with. Technically DJ Lightning Lance is the first DJ to scratch on a record, but like I said, those Live Convention albums weren't official. Grandwizard Theodore, who invented scratching is on the Wildstyle Soundtrack)