You've probably realised by now, there's no hard and fast rules.
There's less than perfect L lenses (primes and zooms) fantastic non L lenses (primes and zooms)
Although you'd think that a very wide generalisation would be that prime lenses are better than zoom lenses, L primes are better than non L, L zooms are better than non L. It is a vast generalisation, and then there's how subjective 'better' is; build quality, focus motors, sharpness, colour rendition, edge sharpness, bokeh? What's important to you?
A lens I'd love is the 85L, it has the most wonderful creamy bokeh and razor thin DoF. But it takes for ever to focus and so the hit rate for some people is such that they prefer the much cheaper 1.8 version.