Lol, having seen Wicked 8 times I do indeed disagree with Hannah! If you want a great feel-good show that's very funny and light-hearted, pick Wicked.
And actually, Wicked has some of the cheapest tickets compared to all the other shows - being right on the edge of the stalls still gives a near-perfect view, and it's less than £20.
If you want a long, emotionally charged and slightly sad but ultimately fantastic show (what a mouthful), pick Les Miserables.
If you want a love story with more operatic themes, pick The Phantom of the Opera. I've seen both this and Les Miserables twice!
I haven't seen Mamma Mia or Billy Elliot, though I don't like the films so I won't be seeing them. Legally Blonde will indeed be closed. Wizard of Oz is meant to be excellent though!
As for The Lion King, I enjoyed it as a production, but the songs aren't good enough for me to call it a 'musical', silly as that might sound.
So yeah, I would recommend Wicked, Les Miserables or Phantom of the Opera