Great Artists with one great record

I was listening to Anita Baker's Rapture recently, and I was shocked to think the record is 27 yrs old, and she has really had nothing anywhere near the same level since.

This woman has one of the great voices I have ever heard, yet only has one record I have heard that is worth a listen. Are there any other artists you can think of that have not really come near their potential more than once?

Why can't someone take this woman into the studio, give her some songs, and make a great record??