Need your help to pick the next project!

I only ever work on two projects at a time. The book I am currently writing, Proper Darkness, and the next book I am outlining. I have not decided on the next one to outline. All of the stories I propose are the kind of stories I love to read.

The Outlining Process I use begins with a short description of the book. The four listed below are the leading contenders for the queue: 

Proper Darkness by Martin Wilsey

1) The Zombie Novel: When a newly married couple returns from their camping honeymoon in the Rockies they find Denver in flames and the dead walking the streets. Can they figure out what happened and find a way to survive with death pressing in from the living as well as the dead?

2) The Time Travel Novel: When a widower tries to find himself again on a Trans-Pacific race, alone on a damaged sailboat, in the middle of the Pacific he stumbles into a conspiracy that if it goes wrong could destroy all of mankind and even Time itself.

3) The Alien Mystery: When a quiet groundskeeper of a historic cemetery in Richmond VA discovers the bodies of six executed Police officers, he must hide who he is as long as he can, or it will mark just the beginning of dark times for us all. 

4) The Haunted Spaceship: When a deep space salvage team discovers a giant derelict ship, Captain Adriana Fischer must decide if the haunted vessel is too good to be true when her crew begins to disappear one at a time.

--Which one would you pick? Let me know in the comments!