> there are times when it can be as complex as any of the works you mentioned, the time involved in writing scores is often very short

Mozart composed his last three symphonies in less than a month and his requiem in two weeks. Rossini composed Barber of Seville in less than three weeks. Bach composed cantatas (30 minutes each) by week... The list goes on and on...

And please, dont even say that a film music score by Williams or Goldsmith can be as complex as a Wagner opera or a Mahler symphony. This is a very simple kind of music that sounds great and complex only to the vulgar ear.

In the film music genre i only consider two masterpieces and one great great great job: Alexander Nevsky, Ivan the Terrible and Cutthroat Island.