Is there gitg for windows?

There is now an installer available for gitg on windows

http://ftp.gnome.org/pub/GNOME/binaries/win64/gitg/

You may find it a bit hard to port it. Here's what the author has to say about the portability of gitg (source):

gitg is a git repository viewer targeting GTK+ and GNOME. One of its main objectives is to provide a more unified user experience for git frontends across multiple desktops. It does this not be writing a cross-platform application, but by close collaboration with similar clients for other operating systems (like GitX for OS X).

I'm sure it's still doable. But it's definitely up to someone else to do it. So you shouldn't probably expect a port to windows anytime soon. Alternatively you can always run it from Windows with tools such as:

• Wubi, or
• andLinux