To add to Blackace's comments, the IL2 series are quite something (Pacific Fighters and Secret Weapons of the Luftwaffe being the most recent - I think if you buy the latter you get all of the previous stuff as well).
Rumours are out there that there is a Battle of Britain version on the stocks ready for launch around July time that is even better than the IL2 series - same people (Oleg Maddox and Ubisoft) as well.