GNOME 3 gnome-fallback is the only way that's official to use GNOME 3 with Gnome 2 like desktop experience. Another existed fork of Gnome 2 is not officially supported by GNOME developer, that means we could use that but with its our own risks about unstability. In Ubuntu, this desktop is installable by apt : sudo apt-get install gnome-session-fallback.
But, there is one bad unfixed look in GNOME 3 gnome-fallback desktop : the top panel looks so big and so ugly (fixed at size 30 pixels and unable to resize by alt+right click>properties). But apparently, there is a way to fix this appearance problem, and this is the way :
1. Open Home, unhide hidden folders by clicking menu View>Show Hidden Files or press Ctrl+H.
2. In the .config folder, create a new folder gtk-3.0, and then create a file settings.ini.
3. Next, edit file settings.ini and put this lines :
gtk-icon-sizes = panel-menu=16,16:gtk-large-toolbar=16,16
Save and Close.
4. Logout and login back.
Enjoy ! :D