If you don't have a wide sweet spot, are you really an audiophile?

In short if you want a wide "sweat spot" get a speaker that does not image and you will have the widest sweat spot imaginable.

Anybody who thinks they have a wide sweet spot either does not know how to evaluate an image or has no sweet spot at all. High frequencies blasted all over the room does not constitute a sweet spot. It is all about the image not dispersion. 

@erik_squires,@erik_squires, I think you are confusing image specificity with frequency response. Sanders ESLs beam like crazy. You will only get high end directly in front of them but because they beam there is much less room interaction and their image specificity is excellent at the listening position. Move of center and the image falls apart as well as the high end rolls off. Speakers with wide dispersion will sound balanced over a wider area but they also have more room interaction. The on center image is not as specific as the Sanders but it still falls apart off center just the same. The high end just does not roll off. You may not notice the image falling apart as much because the image is not as specific on center. What you really want is a crossoverless ESL with a 45 degree dispersion angle. You will get the sharpest on center image with reasonable frequency response across the listening area. The physics of a two channel audio system are such that the only place you are going to get an accurate image is on the center line. That vast majority of systems do not have a very specific image. This is because of the speaker's dispersion, room acoustics, phasing and time problems and asymmetrical frequency response of the two channels.  

Read about Ambiophonics.

Audio2design, thank you for your post. You are mostly right. It is all about timing and volume. You are also probably right about certain situations.
The vast majority of recording is done multi micing, not with stereo microphones. Then it becomes all about volume differentials between the channels, to where the sound was mixed. Now the timing event becomes paramount and that can happen only when your head is equidistant from the speakers that are properly balance (volume) Unless you prefer to go the ambisonic route. Your central nervous system was designed to work with head shading. It increases the volume differential between the ears allowing more accurate location of the threat. Timing also changes. In order to produce an accurate image you have to be equidistant from speakers balance correctly and both speakers have to have the exact same frequency response curve. Very few systems meet all these criteria and do not image as well as is theoretically possible. Yes, the way the recording was done influences all of this. 
With a good system one can sit comfortable in a chair and enjoy an accurate image. If you move side to side enough you will hear the center image melt. With line source speakers you can move all the way to a side wall and the instruments mixed to the other side will still be loud and clear coming from that side as if you were at a concert but the center image will be vague. With point source speaker the volume drops off much more acutely with distance so the center image shifts entirely to the side you are on including instruments in the center channel but mixed a little to the opposite side.

I use line source ESLs which have been digitally corrected and produce identical frequency response curves. I frequently have to adjust the balance with different records a few dB to improve the focus, something you would never notice in most systems because the image specificity is just not there. Volume and timing have to match up!
As you would expect some recordings produce better images than others. Mono records can not be listened to from the listening position.
It sounds like you are listening through a crack in a door, weird. I sit off center when I listen to mono. Everything opens up. 
I have listened to corrected point source speakers particularly a friends Watt/Puppy JL Audio subwoofer system and dead on center it produces a beautiful miniature image. Move off center and it falls apart as you would expect. 
It is sort of the exact opposite of what the OP says, the more noticeable the sweet spot the better the system. If you can not differentiate the exact center from two feet over your system is not imaging. Some people may be happier this way. Ignorance is bliss.