Had Mclaren actually sided with either drivers in 2007, Alonso would’ve many races Hamilton did based on pure favoritism, most notably Indianapolis & Hungary. Thus, he would have been champion that season.
I think Alonso would have had a great chance of winning in 2008. Hamilton made quite a bit more errors in his second year than his first ironically. The main reason to why Fernando had such a hard time against Lewis in his rookie season was because Lewis didn’t drive like one, he was practically flawless and probably more consistent than Alonso that year.
In my opinion, if Mclaren favored Alonso and he kept his head cool he also would’ve won championships in 2007, 2008, and arguably 2010. He also would have given Vettel a much closer run for his money in 2011. Of course, all we can do is predict what would have happened, we’ll never actually know…