Gnome in your Ubuntu, or just find out LightDM is not your favorite, then you can change your login manager. Here is how:
in terminal type:
sudo apt-get install gdm
then type your password and wait for the software being installed.
After that, type
sudo dpkg-reconfigure gdm
and choose GDM from menu
For the changes to take effect, restart your computer.
If you want your LightDM back, type
sudo dpkg-reconfigure lightdm
in console again.