Yes, but was Doolittle the last surviving GO?
It's hard to tell who was the last.
You can find lists of three and four and five star generals online.
It's harder to find lists of Brigadier Generals.
You can get the lists of 4 star generals from Wikipedia and backtrack to try to discover when they got their first star.
The US Army Airforce may be your best bet, since young officers rose quickly there.
For example, Dean C. Strother was made a USAAF Brigadier General in 1943 and died in 2000.
Robert Merrill Lee was made Brigadier General in 1945 and passed away in 2003.
Air Force General William Momyer died last month. No word on whether he got his star during the war or after it. So in theory, there could still be a surviving WWII general still alive somewhere.