codec? x264 and 1080p is in the ~8GB range for a 120min movie. Depending on audio might be more.
VC-1, H.264 (MPEG-4 AVC)
Also, the studio paid a professional to peep at all the inter-frame pixels and turn the knobs right when they encoded the bluray. I might be able to get a perceptually lossless rip that's 25-50% smaller than the original, but it's just not worth my time.