If the decision on lens purchases is based on web-based research, most likely only the lenses that produce high MTF, low distortion, and low chromatic aberation numbers will be judged "great". And each manufacturer has produced very few lens models that have achieved "greatness".
But if instead I look at whether a lens produces the type of image I want, the range of choices expands GREATLY. In the case of Nikkors for example - I find that some of their Series E lenses produce really wonderful images. These lenses are considered the low end cheap glass of Nikon. But it turns out that they do a super job for ME. But then I'm rarely wanting my images to produce clinical perfection... imagery like that doesn't express how I feel about the world.