I wouldn't recommend symlinking another terminal app to gnome-terminal. If any other application in the system is trying to invoke gnome-terminal with specific parameters this might fail. On top of that symlinking might cause issues with package/system upgrade.
Simply keep your favorite terminal app (terminator/tilda/guake etc) in ubuntu dock/start menu. The other option is to configure nautilus file manager to open your favorite terminal. I presume this is the most likely use case for most people anyway.
sudo apt-get install nautilus-open-terminal nautilus-actions
