Nothing is best
No anti virus is fully perfect...
1)Norton does not detect a virus embedded in a file(merged with another exe)
2)Mcafee does not detect at all(Stinger is an exception)
3)Zonealarm is prone to ack flooding and it can also be patched using runtime infection techniques8)
4)McAfee Firewall and tiny firewall are also of no use.
5)Norton Av can also be finsihed by using a program newly designed ..Dun wanna mention the name
So kasperksy can also be defeated in the mere future 8)