There is no direct answer to this question. Asus ROG / Zephyrus tops the list in motherboard failures. That's what we see in our shop the most. HP spectre comes next then dell Alienware. All 3 brands are very popular and what people tend to buy the most.. It could be the reason why we see many of these brands in particular. 

Working in the electronics repair business for almost 40 years, I can't tell you how many times I have ben asked similar questions.  As Alex stated, there is no real answer to this question.  As a warranty station for some manufacturers, I would be asked about reliability of the brand I service.  Again here there is no real answer as the only units I saw required service.  There was no way for me to know how often these failed as I never saw the ones that worked well.  As a service provider, our perspective is skewed.  We can indicate what brands/models we see the most, but there is no correlation between this and quality or reliability overall.

We can indicate what things are easy to repair and perhaps upgrade to use better quality parts. Perhaps the best way to determine quality is to track newer models to see if changes were made by the manufacturer to address what appear to be design or quality flaws in newer products.