I hear the New High End LCD's, probably something like 700:1 contrast and 8ms response time, is pritty comperable to Standard CRT's graphic wise.
But that is just the Natural charecturistics of LCD's... They make Text appear Sharper, but graphics may look more jaggid without anti-aliasing enabled. The imperfections in Graphic programs show up more on LCD because the pixels are closer together.
Also... you will notice a Graphic color difference if you run your aplications in 16bit color instead of 32bit on a LCD, but you wont on a CRT. go to your Display settings and check and see witch color depth your Desktop is set at.. and also in game settings.
conserning your FPS game performance... Maybe you forgot to install your Motherboard Chipset Drivers? no?
EDIT: o yea, a monitor cannot affect game performance. and your 13" old monitor looks better graphic wise, becuase its CRT, and the smaller the screen the clearer images may apear because theres less pixels so the image isnt expanded as much for you to see imperfections.