Well I believe with DCS WW2 they are trying to take on that goal. With all of the WW2 planes being developed and the Normandy map, I can see it being very complete and realistic. I think it will be a lot of fun. Especially using the AI b-17s. Attacking or defending them with the proper planes will be a blast.
They other "world' is probably the modern day stuff, which is complemented fairly decently with the A10, FC3, and what not. Even some of the other companies like VEAO, making the Typhoon and A4 Skyhawk will fit in very nicely.
What really will be the "oddball" is the Sabre and unfortunately Mig-21.... Wihile mig-21 is still in modern day use, the aircraft is almost useless against more modern fighters.
Sabre would need Korean theatre, Mig need possibly vietnam. These could occur with time as Edge is release, however I really am most interested in WW2 and the modern stuff