Our Janet Jackson Vintage Pop Stardom Week continues in 1990, with the pop legend returning from her 'Rhythm Nation' peak somehow even bigger and more iconic than ever. Janet Jackson on the set of her film 'Poetic Justice' (directed by John Singleton), 1993. Anthony Barboza/Getty Images Trending on Billboard In honor of her upcoming 60th birthday this Saturday (May 16), we’re doing  a full week  of  Vintage Pop Stardom  deep dives into the all-time greatness of  Janet Jackson  on the  Greatest Pop Stars  podcast.  Each day this week (May 11-15), we’ll look at a different peak year in Janet Jackson’s singular career —  1986 , 1990 , 1993, 1998 and 2001 — and hit on all the albums, singles, videos, dance routines, tours, performances, fashion statements, social and political statements, and other big moments that made Ms. Jackson’s contributions to the music and culture of those years absolutely unforgettable.…