If you want a 20" 1600*1200 LCD (non-widescreen), I'd suggest the following:
=> Samsung 204B (5 ms TN panel)
+ very good response time, suitable even for fast games
+ pretty good colors and contrast for a TN panel
+ inexpensive
+ tilt, swivel, pivot, height adjustment
- 6-bit color with dithering
- poor vertical viewing angle
- some noise in videos
- foot not super stable
=> ViewSonic VP2030B (8 ms g2g 16 ms bwb P-MVA panel)
+ pretty good response time, suitable for all games, faster than 8 ms S-PVA
+ good colors and contrast
+ tilt, swivel, pivot, height adjustment
+ great video playback with low noise
- stable foot but large footprint
- slower than TN panels in games, some minor ghosting possible
- backlight issues possible
- risk of encountering input lag
- quite expensive
=> NEC LCD2080UXi (16 ms S-IPS panel)
+ great colors
+ fantastic viewing angles
+ tilt, swivel, pivot, height adjustment
- slower than TN and fastest VA panels for games, some ghosting possible
- buzzing noise reported at lowered brightness
- expensive
- "shimmering effect" typical for IPS panels
- considerable noise in videos
If your main focus is gaming and you can sit dead on in front of the monitor, I'd recommend the 204B. Stay away from Samsung 204T - it's slow for games.