Sales figures are sales figures. If that is the measure of success so be it.
All three of the majors are equally good, what is a strong point in one is a weak point in another.
If you make any major purchase such as a truck based on sales figures or blind brand loyalty you are an idiot plain and simple.
I have had GM,s now I have a Ram. Why did I buy a Ram,because my gut told me it was a good vehicle and so far my gut has been right. Next truck I will test drive all three and I will go with my gut once again.
Is there a source for retail sales, the picture may be significantly different if you pull out fleet sales. I remember 30 or so years ago Goodyear tire advertised one of their tires as being the sales leader. Goodyear failed to mention that they had landed an OEM contract with both Ford and Chrysler, take away the contract tires and the figures changed considerably. I had them OEM on a Ford Ranger and they sucked in every aspect but longevity.