Not sure I can narrow it down to three, so I am going to cheat a bit by lumping a couple together.

1. Spooky to complete the slasher trilogy with Nightmare on Elm St and Friday the 13th. I would LOVE to see those lined up next to my Halloween. Lots of other horror franchises would be cool (Phantasm practically writes itself, Evil Dead, Scream, etc), but those two would be instant buys for me.
2. Harry Potter
3. A few Nintendo properties would be awesome...Metroid and Zelda in particular, but a modern Mario would print money. I would have loved to see Cosmic Cart Racing themed as F-Zero.

And one more cheat/honorable mention...The World of Dr Seuss. So many possibilities. And someone finish Alice in Wonderland please. And a modern Haunted House...