I'm currently using Ubuntu GNOME 16.10. I love the GNOME DE. I like it much better than Unity. But the one thing I like about Unity is the login screen. I know it's possible to get LightDM for GNOME, but can I get it to be exactly like the login screen for Ubuntu?
Yes, if you change from the gdm3 display manager to the lightdm display manager, you'll get back your favorite login screen again.
sudo dpkg-reconfigure lightdm
and choose lightdm.
For more info about this command, see