It's a pointless exercise, because most responders (a) don't know everything about every composer*, (b) are simply going to go for their favourites. Not possible to be objective. In terms of classical composers, there's almost a consensus abroad that Bach, Mozart and Beethoven are right up there.

I can't understand why Wagner and Britten are there in the list at all, but note my total lack of objectivity.

I listened to Benjamin Grosvenor playing Schumann's Kreisleriana yesterday, and for half an hour Schumann was my favourite composer. But Beethoven is my man. But what do I know of all those 20th century modernists? Not a lot, because I turn the radio off when they come on. It's all a bit whimsical, but I suppose whimsy is an important part of being human...

*A fellow teacher once told me that stairway To Heaven was the greatest song ever written. I asked him if he'd heard every song ever written...