Emacs doesn't play super well with others. You can do a lot of things in emacs, but you can't do emacs in other things.
On the occasions that I'm writing Java, I find IntelliJ to be super awesome. But I get annoyed because the editor in IntelliJ is not emacs. I'd like to be able to do things I can do in emacs in IntelliJ. Realistically, that means replacing the IntelliJ editor with emacs, but at the moment that isn't really possible.
Some things you can use emacs for, like editing web forms (I used to do that with an extension in Firefox), but emacs is really not so great at being used in other programs.
As far as emacs itself, the somewhat crappy GUI rendering precludes creating an IntelliJ like experience.