I tend to agree, the best FM and DM in the world alone, or the best graphics alone won't do much for a sim. The reason is because they need to be combined to give you the all important feeling of an immersive experience. There's nothing better than feeling you are really there. Well, short of a 20mm shell exploding behind your chair
How many here remember European Air War? It's a very old game and certainly not up to par with IL-2 in the technical aspect, but i would find myself reinstalling it from time to time because of immersion alone.
I had seen HUGE battles with about 200 planes in the air at the same time and the AI wingmen radio chatter was so realistic i almost fell sorry about them when they would get shot down. Certainly one of the best sims ever made as far as immersion goes.