Which of these monitors is best? 10,000,000:1 ?

That would be the dynamic contrast ratio, and it is genuinely useless when it comes to comparing monitors.

Also, two of your three (the first and the third) are the exact same monitor. Between the first and the second, the differences that I can see are:

1) Size. They have the same resolution, but one is 21.5, one is 23.6 inches.
2) Backlight. The 23.6" appears to use CCFL, while the 21.5 uses LED.