Where to even begin? MOO2 is one of those exceptional and rare classics like MOM, Warcraft 2, Act Raiser, Ogre Battle, etc.
One thing about MOO2 like the other games mentioned that stands out is the entire package was nicley done. The atmosphere, graphics, music, etc. all comes together to make the whole better than the parts. For example, the music and sort of dark and high tech atmosphere portrayed in MOO2 really made me feel like I was leading a galatic empire through desperate times.
Of course, the game play was also fun and stategic. You could design ships, and space battles were a lot of fun. Also, planatary invasion graphics were better than they were for galciv 2.