How do I make all file types open in the internal editor in eclipse?

The problem with this is that when Eclipse doesn't know what to do with a given file, it opens it with the so called "System Editor", which actually is... whatever your OS says it is, hence the "rolling dice effect". I don't think you can tell the OS to use Eclipse as the default editor (though I didn't try; anyway I wonder why anyone would actually want to do it), so you have two alternatives: either install an eclipse plug-in to manage the kind of file you want to edit (like e.g. pyDev for python), or go to Window > Preferences > Editors > File Associations and associate your file extensions to the built-in text editor in Eclipse.

I happen to be a heavy user of Vim, Emacs and Eclipse, and for this job Emacs is definitely not what you really want, though if you want to try it for its own merits, Emacs can substitute Vim quite well (modal interface and all), look for viper and vimpulse.

FYI: I came here after reading your post

I have the same pain. You might want to add the extensions you want to open with the internal editor to Eclipse's "File Associations". They are found (in my MacOS version) in Preferences>General>Editors>File Associations, list the types you want opened internally, and chose "Text Editor (defalut)" as "Associated editors". I hope this helps.