I have GT5 and owned FM4. Though Forza was fun for the first few hours, after that I noticed certain driving flaws that I just got irritated. GT5 also has it flaws but at least driving was much better, GT6 has even better handling of cars however not all the content has the same quality (mostly graphics) but it still has much more content than any racegame.
Overall presentation is the only thing forza wins but it lacks content and some things look far better in GT6 (premium car models and tracks, lighting), Driving simulation wins GT6 over any racegame ever on console.
Stories unfolded with my home made rap songs. Feel free to listen here with lyrics: https://youtu.be/vyT9PbK5_T0







