Recent versions of Ubuntu is coming with Unity desktop which are bit heavy.
We can also install gnome classic from command line.
To install gnome classic or gnome session fallback use following command:
$ sudo apt-get install gnome-session-fallback
After installing just logout from this session and relogin.
Before logging in click the icon(Ubuntu Icon) in the top right of the Login box and select Gnome classic and login to you account.
This will take to gnome classic desktop.