Toss up between the first and third. They are both brilliant pieces of work. Aliens has too many bits of temp track copying and "homage" (read: polite way of saying Horner ripped off other works, including his own). Still a terrifically exciting and colorful score, though. Resurrection is very good and works great on disc in its complete form, but its not quite in the league of the first three. And Prometheus has some good bits but is mostly dull modern score writing, flatly mixed and recorded. I like Streitenfeld's original main theme a good deal (shows up in "A Planet", "Space Jockey", etc), before it was shafted for the new Star Trek-y "Life" theme.