I have a problem with a lot of rap albums, none of the songs feel like they were made to be put on the same album. Too often rap albums sound like greatest hits albums. It's not a deal breaker but I'd rather not get that feeling when I listen to music. Many artists avoid that problem by adding some loose narrative (Deltron 3030 and Disposable Arts come to mind), others just write songs that sound good together. Gang Starr took the latter to new a level with Step In The Arena.
Every song is apart of a greater whole, married to the themes present throughout the album. Guru brings lyrical diversity with no shortage of rap braggadocio while DJ Premier made sure every track was scratched to hell and back. It was unprecedented 17 years ago and 17 years later it's unrivaled. It's no wonder why IGN called it the number 1 rap album.