Comparing WoW to IL2 could be more comparing apples and oranges. I wonder how many people play WoW only offline?
So comparing the online-numbers of a 9 year old engine to a 3 year old massive-multiplayer-game is the same as saying there are only 30 people a day eating a pizza in the local restaurant, but millions eating each day at McDonalds worldwide.
That doesn't tell you anything about the quality of the food nor does it give you a basis of which is more likely to stay in business or if those making the food can live from the money they earn.