Is Emacs an IDE? Here's one answer. Here's another: who knows, who cares? You might as well ask if Emacs is a fingdop. Emacs is what it is regardless of whether or not we call it an IDE (or fingdop, for that matter). It's hard to see how a decisive answer to the question would make the slightest bit of difference in anyone's life. I don't understand why people keep obsessing about this.
Here's what Emacs is: an editor that provides a user programmable editing environment unmatched by any other editing tool. Sometimes it looks like an IDE, sometimes it looks like an operating system, sometimes it just looks like an editor. If you simply must feel like you're using an IDE, fire up Eclipse; then there'll be no doubt. Just don't blame me if you still aren't happy.