Battle of Britain 2: Wings of Victory is very good, though it only does Battle of Brittain but does this very well, great 100+ plane airbattles.
I'm probably the only person in the world that doesn't like IL-2 1946 very much, imo it is very unbalanced and I don't recommend it for singleplayer. On the other hand the graphics are still very nice and it's plane handling is very convincing in general, but other than that, meh.
European Air War has the best European theater expect 100+ plane battles over Europe, it even has a SWOTL mod, but it is also very dated, flightmodeling and graphics is sub par if your used to post 2000 sims.
Another personal favorite of mine is Fighter Squadron: SDOE, it had the best WW2 flight modelling of its time, only campaigns and maps were very limited in scope. Maybe it can be solved with modding, but I haven't tried that yet.

BoB 2. Wish there was more.

It has tons of mods, even it's own full conversion WW1 mod:

http://www.moddb.com/games/fighter-squadron-screamin-demons-over-europe

The limit on map size for SDOE has also been overcome, but so far the
tiling is still a limiting factor for terrain detail, so most large
terrains are either mostly water or mostly monotonous forest/steppe.

I read about an expansion to BoB2 about the Flying Tigers. That would have been amazing in BoB2's engine.

Anyway, not sure whatever happened to it. IL2 is overwhelming to me and I can't seem to figure out what combinations of mods and tweaks to the enjoyr campaign thingy to make it all work. BoB2 seems straightforward by comparison and has some tough AI.

The FT project was to be a collaboration with Jason @ 777, and
it was discussed here but I can't seem to get any hits now on
a search for it. Basically it was "shelved". As I say if I could
find the posts from Jason I would link them. I think an approximate
paraphrase was that they felt they didn't have the funds to put up
the necessary coding manpower to whip it into shape at the level
of quality they wanted to deliver, so they made a tactical withdrawal.

I seem to recall also that the gist of the message was something like,
we haven't given up on the idea of creating a sim, but not this one, not now.