Alan Silvestri is easily one of the best fantasy/ adventure composers today, his scores are always momumental in scope (The Abyss)Frantic and wonderfully loud and exciting (The Mummy Returns)and always seem to have a wonderfully magical quality to them (Back To The Future and Who Framed Roger Rabbit).
Also Silvestri always manages to come up with great themes and even when the theme is not that strong he gives them such a performence you remember them as good anyway (Judge Dredd).
With out doubt Alan silvestri is one of the greatest composers of the age alongside David Arnold, John Williams, Jerry Goldsmith and James Horner oh and Brad Fiedel (Well he did write the Terminator Theme after all, you've gotta give him credit for that, but not much else).