It sounds like you have setup runlevel 5 (i.e. graphical login) just fine. Normally to access the GUI you'd have a monitor hooked up to the system or allow X connections over the network via XDM or the like.
The following assumes you have a vnc server running. This is a pretty good assumption as you show it running with your command.
I would guess that the issue is that iptables (the host based firewall on linux) is blocking access for the vnc server.
You can run the following command (this will open access to the whole network):
/sbin/iptables -I INPUT -m tcp -p tcp --dport 5900 -j ACCEPT
If you want only from a specific machine or network then use this rule but substitute MY_NETWORK for the ipaddres or cidr block that you want to allow:
/sbin/iptables -I INPUT -m tcp -p tcp --dport 5900 --src MY_NETWORK -j ACCEPT
Try to connect again with VNC. If everything works then you can save your iptables changes like so:
/bin/cp /etc/sysconfig/iptables /etc/sysconfig/iptables-`date -I`
/sbin/iptables-save > /etc/sysconfig/iptables
This will make a backup of your current iptables config and then write out the new one.