I'd argue Paladins should go Strength to at-least open up mutli-classing opportunities later. If you go Dex you can't mutli-class period.The only class that should be strength based is Barbarian.
Best fighter is dex based, best ranger is dex based, best cleric is wisdom based with dex as a secondary/tertiary.
Paladins can go either way probably better strength based but that's debatable as well.
What are we determining 'best' for Fighter and Cleric? Fighter seems quite shakey as a lot of powerful weapons are Strength based ones, and not every party needs a Fighter who is ranged.
Can't argue with Ranger for obvious reasons, Cleric I am unsure about, depending on what Subclass is considered the 'best'.