I've only seen:
Cats (tour cast)
Chicago (tour cast)
Hairspray (Bway)
Rent (tour)
The Drowsy Chaperone (tour)
Avenue Q (Bway)
and this coming May, Wicked (west end)
I've seen quite a few shows on Broadway since I live so close to the city but my absolute favorites are
Legally Blonde (I'm so sad that it ended)
Mary Poppins
Little Mermaid
and Hairspray
I like Chicago, Rent, and Phantom too but they're a little to dark for me.
I love upbeat musicals/plays.