Please, enlighten me. If submarines played such a good role in WWII, name one occasion off the top of your head where a submarine caused an astounding upset in the outcome of a battle or the entire war.
I hate defending Stealth, but that isn't a fair question. Submarines were never designed to control a water way but were instead used to destroy the vital supply lines necessary to a nation. Sure there were a few submarines that successfully attacked and sank capital ships (Royal Oak, Yorktown, Ark Royal, etc) but that isn't their role.
If Germany had focused their efforts on a submarine force and it was large enough to make Donitz happy at war start (300+ boats), I'm certain the Battle of the Atlantic would of forced Britain to seek some peaceful arrangement out of necessity. I am not implying they would surrender, submarines aren't by themselves war winners, you still need something that can dominate/control the water.
However until Aces High gets a merchant fleet to interdict, it is pretty useless for submarines to make an appearance.
edit: too busy at work, AKAK beat me to it.