Unity can make pretty much any game you can think of. It can render pretty much however you want, in 2D or 3D, in first person or 3rd Person cameras, and with whatever game rules, controls, and other stuff you might wanna do.
Q-Gears has the distinct goal of being able to play FF7 from the original data files. Most of the work that goes in it is not into things like rendering, but into reading and reverse engineering FF7's data (as well as other Squaresoft PSX engines). While it will also be much easier to make an entirely new game than by just modding ff7 into something different, that is not its most immediate purpose.