Hades and Zeus Part 1 were my favorite from GoW3. Zeus Part 2 and 3 and 4 were.... meh. GoW2 my favorite fight was with Lahkesis, hands down.
There are 2 boss fights I hate so much on God of War 3: 1. The dude who runs away from you like a little bitch (I forgot his name) 2. The humongous crystal scorpion.
GoW2 my favorite fight was with Lahkesis, hands down.