I learned a valuable lesson when I saw Beauty and the Beast four years ago: don't see anything after it's run about three years: the show gets tired and the director probably doesn't police his work, taking out all the garbage that's been added by the cast. Beauty and the Beast is now a theme-park attraction. The Lion King has now run a decade, although I suspect Julie Taymor keeps an eye on it, so it may not be as tired as B & B.
I'd recommend Avenue Q or Mamma Mia, which are both a pleasure to see. The score for The Drowsy Chaperone is terrific, but Grey Gardens is a fascinating idea. I plan to see it in April.
I'd recommend A Chorus Line, partly because it is a piece of theatre history as well as a musical any fan should see.
I've seen Mamma Mia four times (Minneapolis, London and twice in New York) and really love it. I saw Mary Poppins twice in London, and really thought it was great.
I'd see that, too.
Good luck.
NYC Visitor and Broadway Fan