If I understand what he's saying: Can a 1Ghz system perform faster than a 2Ghz system, all other things held equal?
In which case, yes, that is possible. If the architecture of the 1Ghz system allows it to process more than twice the amount of information per cycle than the 2Ghz system, then it would still perform better.
To give you a real-world example: ~2.0Ghz Athlon 64s were giving ~3Ghz P4s a run for the money when they arrived, and the Core2Duos are continuing that trend. This is a Wiki on IPC, or "Instructions Per Cycle," and it offers a good description of how a slower frequency system can outperform a higher frequency system.