It's hard to answer "best." One of the first that I was pretty bowled over by was seeing my grandmother in Man of La Mancha. (My grandmother was a professional singer, and has six Broadway credits to her name.)
|She was the Housekeeper! (Yes, it was a singing role.)|
Grandma is also on the CD.
I have also seen Wicked twice, Avenue Q, Spamalot, A Gentleman's Guide to Love and Murder on Broadway, Les Misérables, Rent, The Book of Mormon, and a couple really cool local productions of Rosencrantz and Guildenstern are Dead, Fiddler on the Roof, and 5 Lesbians Eating a Quiche. I saw a college cast perform The Rocky Horror Picture Show, Home, Dracula, and Jeffrey.
But one of the definitely coolest theatrical presentations I've seen has been the couple Welcome to Night Vale shows I've seen.
This is usually a sound-only show that you listen to on a podcast, so seeing it actually performed is a fun treat (though for the most part the folks playing the roles are not participating in traditional acting, and they read from scripts and perform very few physical cues). My friends and I really like Night Vale and regularly check out their events when they travel near us.
I was sort of in a play once. I got type-cast as Cinderella because I had the smallest foot.