It's an interesting marketing game.
F-series is indeed the best selling nameplate. That includes the 1/2 ton F-150.
Many (most?) of those 40 years, GM sold more 1/2 tons than Ford, but it was on 2 nameplates.
Why does GM keep 2 namesplates? One of the reasons is to market the 'oldest nameplate' (GMC). But they always sells more Chev Siverados than GMC Sierras.
The makers usually introduce significant model changes in different years. Often the model that is changed is the one that gets the 'vehicle of the year' for category award. (but not always).
The whole process creates interest and sells magazines -- even if it doesn't sell vehicles, and even if the journalists are wrong.
Motor Trend truck of the year - http://www.motortrend.com/awards/bes...k-of-the-year/
Truck Trend truck of the year - http://www.trucktrend.com/truck-of-the-year/
NAIAS (Detroit Auto show) - http://northamericancaroftheyear.org/
Ridgeline is the 2017 winner at the this years Detroit auto show.
There are numerous news articles, as well as the NAIAS link above.