its all down to personal preference, I like a very contrasty picture so I like to have a higher contrast ratio, while others may like it a little lighter.
I have found that these are good specs to look for:
Colors: 16M+ (almost all)
Brightness: 250+ (though I just went from 300 to 250 and the new ones are a lot brighter seeming due to LED's and truer whites)
Contrast (dyn): Ignore this bleep it doesnt mean a thing
Contrast (typ): 1000:1+
Response time: 8ms (GTG) or lower
Let me explain the contrast, you will find monitors with contrast ratios rated at 10,000,000:1 (600:1) while initially it looks amazing the actual ratio is crappy, look for the highest actual/typical/real/in parentheses number you can, I saw a monitor rated at 15,000:1 (8000:1) this one would look 10 times better than the first one I mentioned. The big number is a light meter held to a white screen, then a black screen, the second is an actual checkerboard on screen so you know the difference between the whites and blacks.
Response time... the GTG means grey to grey (grey to white to grey) I have heard that 5 is the max, I have heard that 8 is the max, I play first person shooters and I use 8ms GTG monitors and they look phenomenal.