I think '20 Excellent' is a stretch. Even the best Web-Based editors are bad. This is why there are so many of them. Nobody has solved this problem well.

From experience, here is what I can recommend and why:

  * TinyMCE - If you need an editor that has many features, go with this. The latest version have improved code output, but it is still questionable.  Of the feature-packed editors it is the most lightweight and produces the best code.

  * WidgEditor - It is ugly by default and has very few features.  It is probably also hard to extend.  That said it produces very clean code.

  * YUI Rich Text Editor - It is comparatively young and still pretty good.  If you use YUI it is probably good enough.