I love RoF, with PWCG (16.1, latest version havea lot of bugs) and the official career the arty spotting and recon missions
The planes are very interesting to fly : I don't know how realistic it is for each plane, but for the case I know best : The breguet 14, this is very representative of pilots accounts.
The graphics are great.
I love the map (especially after modding)
Its drawbacks compared to FE2 and WOFF are the IA and the lack of variety of planes.
At the moment, I play mostly WOFF:UE because I am "playing 1917" based on my current readings WOFF:UE is better for this.
I enjoy FE2 for the planes and all the terrains. But I like it for single missions. TH ecampaign engine has some limitations as the impossibility to modify aircraft formations per period
Also, the terrain engine is outdated, copared to the otehr sims and despite the efforts of the community
So basically, I am happy to have all three of them, the one I play most being a question of "context"