Perspective.
The first years of AW was 2D graphicss that simulated 3D....
Regarding MMOL, Air Warrior is/was the trunk of the tree. Aces High is a result of people fighting over vision, money, rights & attitudes or whatever.... and technically, it's a spin-off that beat the pants off it's conceptual origins. Aces High hit a niche at the right time and place and won the prize. The FM felt very nice regarding realism (to me), which was a huge plus for immersion.
DCS was never intended to ever even BE a WWII Flightsim, although... one could consider it to have been bound to happen eventually. WWII in DCS is essentially an abandoned add-on, something saved by ED as a way of taking care of paying customers. It's taken years, but it's gaining traction with WWII.
The only real problem regarding IL-2 (GREAT BATTLES) is (for me) eye strain brought on by everything in the viewing area being mildly greyed-out. And VR exacerbates the problem. I'm confident there's a setting or fix or workaround (ya ya, I know, I have Reshade), I've just never worried enough about it to take away from my Flight-Time "when" I'm in my IL-2 phase. The plane-set IMO is sufficient, although lacking. That said, I'm pretty sure there will never be a Flightsim that has a plane-set I'm satisfied with. Why the hell hasn't anyone ever done a Do17?? Don't start with Wartunder... just don't.
Aces High is a "Game". Hitech's very own words. Albeit a Game with Flightsim tendencies... it's heavily "Gamed up" far beyond what it ever needed. JMHO but this approach is more a pathogen regarding the current state of AH than graphics ever could be. The approach of what is basically a Sandbox game with "do whatever you want" also invites Capt McGamer to exploit any and every aspect of "the game", inside AND outside the game. Capt McGamer is that disease that shouts "it's MY $14.95" all the way to the ashes of what was once a great thing.... with community support. Kinda earned what is. Just sayin.
IL-2 (GREAT BATTLES) is significantly more advanced than Aces High in Graphics, and quite possibly Flight Model... I'm not sure anyone who hasn't flown a few Warbirds can make a definitive statement in that department. And no, I'm not going to consider a joyride in a P-51 as grounds for a scientific conclusion. IL-2 is still a Game, however far less easily noticeable than Aces High, and it leans more toward the Historical, which speaks to immersion.
DCS is a Flight-Simulation-Game, as best described by one of their Executive Producers when asked directly by 2 (former) Pilot-Youboobers (F-16/F-18) who've spent a bit of doing vids of their DCS experience. The Immersion aspect of DCS outpaces Aces High by Light-Years.
If you're version of Immersion is limited, essentially, to numbers of players in a dogfight, then sure, AH wins. Immersion to some includes getting in as tight as possible with RL... meaning your plane will kill you faster than the enemy if your approach to engine management is limited throttle manipulation. Also, understanding there are consequences to shooting when you don't bother to identify what you're shooting. Just the ATTEMPT of Historical immersion presented by IL-2 & DCS is more advanced than AH.
At the end of the day, if anything interrupted the success of Aces High... it's Wartunder. Easily. AH & WT are in a category, so to speak. So are IL-2 & DCS. There's some bleed-over... but solidly different things.