"Do you know who I am?"
I don't think I framed my thoughts very clearly. It amounts to this.
Imagine a room with a nice big sofa out in the middle of a room. If you have an ideal set of stereo speakers, the person sitting in the middle will get that amazing enveloping sound Franklin describes with nothing more than that. If that same person moves off-axis, the entire illusion disappears and he is left with a very nice sounding front soundstage. If he is not too far off axis, he may still get some imaging. A person on one end of the couch may hear all of the dialog in a movie coming from the closest speaker.
Imagine the same room with a traditional 5.1 setup. The person in the sweet spot will still get the best sound. The difference is that the people who are sitting off-axis will still get the benefit of enveloping sound, thanks to the speakers behind them. They will also benefit from the existence of the center channel, which anchors dialog in the middle, even when you are sitting way off axis.
That is all I'm getting at. The laws of physics preclude the existence of a system that will sound equally good all over a room.
I see your point.... and to some extent I agree with it. But, does it really matter? The story-telling will be the same without the surround effect. It will also be great without the virtual center effect - as long as one can clearly understand the dialog (which isn't hard with a stereo). The bass impact won't be different off axis unless there are incredibly terrible room node extremes, which would be present even with a 7.2.5 system. So, I think the "least worst of all worlds" isn't as advantageous as the best of all worlds for one person.
But maybe I am biased as I never can truly get lost in a movie or tv show to this extent unless I am alone. If I am with another, I cannot help but spend mental energy on thoughts about the other(s) in the room and how they might be reacting. The whole "lost in the content" goes away when there are others in the room.