As far as quality Tamiya is consistently the best imo. Always crisp molds, complete with window masks and metal transfers. Lately Revell has rivaled them with their latest works in my opinion. In a few years I think they will equal them.
Aoshima is also very good. Fujimi has interesting subject matter which is what makes me buy their stuff sometimes. But a lot of their kits, although are crisply molded have inaccuracies and sink marks. They often lack engine detail too. Their enthusiast kits are extremely detailed though the parts fitment isn't very good. But those are old kits so it's understandable.