Well you probably won't find anything as realistic as BS is going to be, but most people would suggest Enemy Engaged: Commanche Hokum 1.9 or LongBow 2 - although neither one is easy to acquire, because they are quite old games.
I only played EECH from that two. It's a 1999(?) game that had its source code released later and is being upgraded ever since by fans. It looks great, have a dynamic campaign engine, and fairly realistic. Current flyables are Mi-28, RAH-66, AH-64 and Ka-52. Every other helo is flyable too, they just don't have a cockpit.