Black Shark is still based on the Lock On engine but with a few dx9 upgrade. Of course this may change over time as the other DCS series comes out.
If you like real simulators, DCS is the best pick hands-down. AC6 and HAWX are both arcade games. Besides, AC6 is a console game, far different that pc games. For pc, we are running on only 32 bit. They could design a computer with a higher bit rate but then most softwares needs to be rewritten. console games on the other hand, could be running as high as 360 bit (hence the name X-box 360). Although their graphics card may not be as good, it still packs a lot of process power and could render a lot of eye-candy shots. But like Pilotasso said, i prefer DCS over graphics anytime of the day.
And with that being said, yes DCS series will be very very realistic. Personally i say a bit more than falcon 4.0 AF with the advance flight model, 6dof, clickable buttons and many more.