Referring to Setup VNC Server at Linux, users sometimes might not able to see a normal desktop in VNC Viewer even though they already uncomment the 2 lines.
It is because /etc/X11/xinit/xinitrc need ROOT privilege to be executed. To overcome the problem, users just need to add the execute privilege for all other users:
chmod 755 /etc/X11/xinit/xinitrc (Red Hat)
sudo chmod 755 /etc/X11/xinit/xinitrc (Ubuntu)
Restart the vncserver and users should able to view a normal desktop in the viewer