I can not honestly answer because I find all theatres fascinating, I have at times loved reading about Arnhem or D-Day or as a young man the Eastern Front. Naval war especially the Battle of the Atlantic is great and how could you not find Dunkirk/Battle of Britain not intriguing?
But at the moment I am fascinated by Burma and a bit by the Aussies in New Guinea including the fate of the POW's. Not sure why perhaps because unlike Europe where it became increasingly massive and mechanised in battles like Kohima individual battalions and even soldiers made a difference and fighting was still deeply personnel -- a Welsh conscript holding a vital fox hole with just his shovel --Freddy Spencer Chapman operating for years behind Japanese lines in Malaya.
Perhaps it was that the environment was as much a hindrance as the enemy, perhaps it was the development of the British whom the Japanese totally out soldiered in Malaya to perhaps the reverse by the end. And the no holds bared nature of the fighting-- the British learnt to fight in the jungle but for instance with the Chindts wounded were often left to their own devices-- sat on a track a bag of food and a weapon, suicide or fight it out. Recently read of one young officer shot in both legs left as such decide either he was not going to die or would at least die trying-- he crawled to Burma!
So many great stories but you can say that of every theatre.