Digital Combat Simulator is a lot closer to a flight simulator than a game. Accurate flight models, fully modeled systems, etc. Each module takes a couple years or so to complete and they are based on surviving aircraft.
Current WWII aircraft:
P-51D https://www.youtube.com/watch?v=pqQrz_EnWF0
TF-51D (weaponless trainer, free)
Bf 109 K-4 https://www.youtube.com/watch?v=n68o3zyXLv4
Fw 190 D-9 https://www.youtube.com/watch?v=nmuDubmrQ-c
Upcoming WWII aircraft:
Spitfire IX (2 weeks) https://www.youtube.com/watch?v=ab_WzkyhiAs
Grumman F8F Bearcat (2017)
Spitfire XIV (2017)
Curtiss P-40F KittyHawk (2017) https://www.youtube.com/watch?v=TxMLKIFao8c
F4U-1 Corsair (Probably 2018 or beyond)
It can get quite expensive to fully get into it. You need to have a decent joystick, some sort of rudder control (preferably pedals, but twist can still work), a throttle is really helpful to have, a head tracking setup, and probably at least a GTX 750Ti.
The planes have enough depth that it really approaches study level sim. There's enough to learn just on systems and general piloting. Pretty sure this is the learning experience on the Dora for anyone that sure, flies in games, but is not a pilot (and maybe even some pilots):
https://www.youtube.com/watch?v=kqTtRXG8n54