Immediately below, from Space Cowboys, and directly below it, the same image overexposed so you can see the blacks as dark grays, and see how overexposed the satellite is. If another projector, with the same black level has a much more overexposed satellite, then that other projector has the better black levels:
Immediately below, is a side-by-side image of the same satellite. The Epson Home Cinema 6500UB (the reigning under $3000 black level champ) on the left, and the BenQ W6000 on the right (you can, of course, click to enlarge). The Epson was not in its "best" movie mode (because the BenQ is much brighter in "best" movie modes), which has some impact. As it turns out, in this photo, the Epson projector is a bit brighter. When you look at black levels though, and compensate for that brightness difference, you realize that the BenQ is close to the Epson. As noted elsewhere, it just depends on the scene, as the two manufacturer irises work a bit differently.
For general black level performance examples we'll start with my favorite, the Starship image found The Fifth Element. The first is our Sony VPL-HW15. Immediately below it, is the Optoma HD8200, . Unfortunately, brightness varies even more (than with the side by side images) on these photos, making accurate comparisons of black levels a little difficult.
The image immediately below is from The Dark Knight. I've intentionally overexposed it to make a point. This is the type of scene where the difference in black level performance makes a huge difference. Because the outside areas of the scene, and for that matter the men's jackets are pretty black, with little detail at all, projectors with just "good" black levels look very flat. Immediately below, is the same scene using the Sony VPL-VW15, which is definitely a direct competitor. Below that one, is a side by side with the Sony on the left, and Epson 6500UB (another direct competitor, although it will soon be replaced by the 8500UB) on the right. Due to the much higher brightness of the BenQ, it wasn't practical to do any side-by-sie comparisons with this scene.