Often in Linux distros root is denied X access (for security reasons) by default.
I believe it is in ubuntu (you have sudo..) I can access X games in opensuse / mandriva as root though.
I it really never a good idea............
To login as root in Ubuntu:-
- login as normal user
- create root password with
sudo passwd root
(type your password - then your new root one..)
Now you can su -
(so although you enter KDE (or if your sick gnome..) as normal user you will have full root access in a console)
- Please note that by default Ubuntu wan't allow root to access X apps, you can always use sudo as normal user though.
However as mentioned loads of times - - it is not a good idea to run games in Linux as root!!