Here I come to throw a curveball, as a FH1 fanboy and FH2-FH4 critic that is falling in love with this game in spite of its considerable issues, playing on PC instead of an Xbox.
It's not the best Horizon ever yet. FH1 still holds that crown for now, so long as there are the issues impacting my solo experience. However, no past FH title can compete with the new handling physics or map in my book. Driving unmodified stock vehicles has never been more rewarding. The driving is better than the racing -- competing with the AI isn't great and everything online is screwed up, but man, the driving experience is pretty close to spot on. 👍
I don't doubt FH5 will be the best Horizon ever for me. It really needs work, though. Not like I expect much better from a modern Western AAA game out of the gate, to be biased.
The market allowed this to become standard.