Blu-Ray Quality Rips

So I download a lot of 1080p BR rips from w-bb. I was wondering, with the variations in sizes (1.5GB all the way up to 20GB), if I am actually getting blu-ray quality. Is there a way to test to see what kind of quality I am getting in comparison to actual blu-ray movies? I watch the rips on my high-end plasma and I am happy with the quality, but I am just curious if it is on par with the real thing, or if the files are just compressed and reduced in quality.
Thanks.
Answer #1
Regular length 1080p movies tend to look best at about 8-12 GiB.
Animated movies tend to be *much* less in size, more in the 5GiB area.