I think Prince is pretty bad artist outside Purple Rain.
The issue is that I think he is a very poor melodist. His melodies are either repetitive, overly conjunct (most of the melodic flow move by steps ), takes up narrow vocal range (although he is capable of wide vocal range due to his falsetto there is lack of vocal leaps or jumping between normal or high voice).
Listening to so called "classic" Prince singles such as "controversy", "Dirty Mind", "red Corvette", "sign o the times" "1999"
makes me completely baffled how they become a hit song as the melodies just seems underwritten. A lot of time Prince even just singing a single note melody. I feel a complete disconnect between myself and popular culture.
Even the repeating riff that some of the songs are based on seems overly underwritten and are at best only marginally better than the nadir of riff based music of Satisfaction by The Rolling Stones (although with that song at least the vocal melodies of the verse is well written even if the chorus is a one note melody)