Hi Scott,
I think none of these really compare to each other.
IL-2 1946 will be the only moddable combat flight simulation to this extent for some time to come, so it will stay alive for much longer than one would think it would considering it's age, the technology behind etc.
IL-2 Great Battles is lightyears ahead technology-wise to any of the games you've listed. You have to play it yourself to see.
Old 1946 farts have to relearn everything from scratch because the immersion and simulation depth is so much more advanced than we used to know it. And that's actually the fun part of it. Believe me, I know what I'm talking about
CFS3 and it's WOFF-UE incarnation are great, they look much better than 1946 does, yet like CloD or e.g. Histomod (which has it's fans not without reason) it will always remain niche product.
WOW looks nearly as great as IL-2 Great Battles does and ships with a planeset that's not too far from IL-2 1946 WW2-wise, and goes far beyond that in other eras, yet it's a pure arcade game. Heck, even the "simulation" mode is arcade compared to any of these.
DCS also looks great, but WW2 is somewhat limited, the development is questionable and the value for money is even worse than it is for the already relatively expensive IL-2 Great Battles series.
To summarize it, IL-2 Great Battles has the best looking graphics of all of these, it's reasonably playable on mediocre hardware, has a very well balanced planeset in all modules, is being
very actively developed and has a great future ahead.
If it would have a "free to play" base module like Rise of Flight had, and if it would be moddable to some extent, IL-2 1946, CFS3, WOFF, WOTR, CloD, Histomod etc. would be dead and abandoned immediately.
Cheers!
Mike