Just to have it mentioned in detail; Fall of the rising sun is the middle way between realistic and difficult, I'd say. It's my favourite up to now and the 1.3 version of it is current for english language. (With 1.4 still in the works.)
Don't forget getting JSGME, a small tool that helps you enable/disable any mods before playing. (Also referred to as Generic Mod Enabler.)
Other than that, have a great time discovering which mod you like best
