You can set the default terminal by changing the alternative for
x-terminal-emulator. Installing gnome-terminal creates an alternative symlink so all you have to do is set it.
sudo update-alternatives --set x-terminal-emulator /usr/bin/gnome-terminal.wrapper
Edit: It seems like the shortcut implementation is not using the alternative, but rather a gsettings configuration. It's still a good idea to set the alternative symlink above, however, to use the keyboard shortcut some gsettings properties will need to be modified. Use dconf-editor (
sudo apt-get install dconf-editor) or gsettings to change the default terminal application to gnome-terminal. You will need to modify the exec and exec-arg properties in the org.gnome.desktop.default-applications.terminal schema.
gsettings set org.gnome.desktop.default-applications.terminal exec gnome-terminal
gsettings set org.gnome.desktop.default-applications.terminal exec-arg ''