Only expensive LCD monitors are really acceptable for gaming. Cheaper LCD monitors do not have a fast enough response time to keep from appearing to smear with fast moving objects on the screen. Another minor issue is that LCDs only have 1 optimal resolution and will not look good at any other resolution.
The key figure(s) to look at on LCDs are:
Response time - The minimum amount of time necessary for a pixel to change. Most cheaper LCDs are sub-25ms response time. The best are rated for 16ms. This is BY FAR the most critical specification from a gamers standpoint. A 25ms LCD will have noticible smearing with fast moving objects on the screen. 25ms = 40 Hz maximum actual pixel refresh rate. 16ms = 62.5 Hz. Note that LCDs do not appear to flicker because of this same issue, they do not have the capability of nearly instantly changing from white to black, which is what causes a CRT to flicker if the refresh rate is set too low.
Optimal Resolution - The resolution at which the LCD will produce the best image quality.
Contrast Ratio - The maximum light intensity ratio between black and white. LCDs cannot display true black, because a portion of the light from the backlight will always get through. If the contrast ratio is very low, text can appear blurred or greyish against a light colored background. You will typically see contrast ratios between 300:1 to 500:1.
If you are looking to buy an LCD, I would recommend looking at the exact LCD you want to buy to check for (annoying) dead pixels or other defects. Also, try to get an idea of response time by moving something quickly across the screen and look for a visible trail. (Playing a video clip or certain screen savers might allow you to judge this in store.)
