Short answer is no.
but it's a bit more complicated than that.
99.95% of computer games can only use 1 core currently. So you only get 1.8Ghz. They don't double up ( and never will, the most you'll get is 33-66% extra processing ability ). So if you have a 1.8Ghz chip which is dual core, you'll only get 1.8Ghz of "speed" out of it for the next couple of year or so (coding for more than one chip is fiendish - the hardware is currently WELL in front of the ability for the coders, especially game coders, to actually use it well )
However, there is light at the end of the tunnel.
Ghz ratings are currently very messed up at the moment. All Ghz ratings that you see on the side of a games box are based on Pentium 4 speeds. So things like 3Ghz etc.
However, the newer chips from Intel (like the Core 2 Duo ) and pretty much any chip from AMD now work in a different way. Instead of working at blistering speeds, they work slower, but do more per process. So a 1.8Ghz Core 2 Duo, or new AMD chip, is going as fast, or faster, than an older 3Ghz Pentium 4 chip and is equivilant or better than 3Ghz.
If you post which chip you have/are thinking of getting, I can give you a better comparison.
Steve