I own several "Classic" and ZM Zeiss lenses.
They are dead sharp, have beautiful colors, a high contrast, and are mechanically "unkaputable".
Yet, this does not apply to every single Zeiss lens. A few zooms designed for Sony were mediocre, to be polite.
Some Zeiss lenses also suffer from flare (50mm Makro Planar) or CA. But, if you carefully select your lenses, Zeiss are often at least as good as their Canon equivalents.
Leica lenses are much more constant in quality, it could be hard to find an "only good" lens from them.
As to Meyers, they have been specifically designed for their special bokeh. So, comparing them to Zeiss, for instance, doesn't make much sense. If you like this bubbly bokeh, go for them. You won't get it with Zeiss. Zeiss are sharper than Meyers, but Meyers are bought for different reasons.