The physics aside, I enjoy the attention to the biological details that is present in the mass effect universe. The descriptions of the physiologies of the various species are quite interesting and are in many ways plausible. It is also nice to see a variation in atmospheric compostion and pressure requirements for each species as well as gravity standards that differ based on the planet where they evolved. Too often these details are overlooked in good science fiction. They even go so far as to include organisms that have evolved based on using the D isomers of the major amino acids instead of L isomers which is fantastic. Of course the likelyhood that all of these species would have evolved to the point of sentience and spaceflight at almost the same time is extremely unlikely but that is easy to overlook thanks to the excellent attention to all of the other details.

The Halo series, especially Halo and Halo 3 have absolutely phenominal soundtracks. The music fits the story, emotion, and action like a glove.