Prince's albums have a lot of diversity over the years. Depends on what you like. I'm particularly fond of 1999 as his classic pop album, but sign-o-the-times is more ecclectic with jazz and funk. While among his least popular, my personal fav is the truth. It was supposed to be a bonus disc on Crystal Ball, but didn't make it for whatever reasons. I adore it because of the excellent recording qualities, it's a mostly acoustic album wich is an oddity for prince, and he clearly doesn't take anything too, too seriously, but shows his chops as a master multi-instrumentalist.

He went through a smooth jazz phase which was respectable, Musicology is another tight album on the pop side of things.