darker eye colors shield your eyes more from bright lights, which is probably why that was the base color for most animals (including humans), however, as Europeans lived in environments with lighter colors due to snow etc lighter eye colors allowed them better cover in their environment than many darker eye colored humans. Like most everything else that can be correlated to particular interbreeding groups of humans in unique geographic regions, there is no out and out superior set of genes, each set is best for a particular environment.