Or speakers that image well and proper placement
The thing is, there is no theoretical reason (or experimental one either) I have ever encountered that would suggest that having only two channels would be better than three, unless there is something wrong with the setup. Why do you think it is an advantage to have only two speakers instead of three? Sure, if the center speaker is bad (or a bad match--try using a different speaker for the right and left channel and see how you like it), or is poorly placed or poorly level matched, then it would make sense that it would be worse. But why would it be worse if an identical speaker was used, and it is properly set up?
Here you can read a pdf about some Bell Laboratory testing that was done on this subject:
http://www.aes.org/aeshc/docs/bell.labs/auditoryperspective.pdf
It is interesting reading. As far as I know, no research since then has come to any fundamentally different conclusion.
For those not going to read the few pages of text, I will give a couple of relevant quotes from
Auditory Perspective-Physical Factors:
The 3-channel system proved definitely superior to the 2-channel by eliminating the recession of the center-stage positions and in reducing the differences in localization for various observing positions.
In other words, one of the advantages of a three speaker system is the "depth" of sound in the center of the stage; a second advantage is improving the consistency of the sound from different listening positions. (People in this thread seem to be aware of only this second advantage.)
Consequently 2-channel reproduction of orchestral music gives good satisfaction, and the difference between it and 3-channel reproduction for music probably is less than for speech reproduction or the reproduction of sounds from moving sources.
2-channel can give a reasonable approximation of the sound, but the important point for the present discussion is that 3-channel reproduction resulted in more realistic reproduction of the sound.
Historically, the reason for two channel systems instead of three is the added cost of a third channel (there was enough question about whether people would pay for two channel reproduction instead of the original single channel audio), and the difficulty in getting a three channel signal on a record for consumer use. And, of course, the setup requires more space in the home, and it is more difficult to properly set up. And 2-channel was judged to be "good enough". It is, however, far from perfect.
We can say, of course, that 2 and 3 channel sound will be different. And it may be that one person will prefer the sound of 2 channels. However, that will not alter the fact that it less closely resembles the sound of actual performers on stage. These days, most people have listened to 2 channel reproduction of sound for most of their lives, and do not regularly listen to actual live music that isn't produced through speakers. So that is likely to be many people's "standard" for what sounds "right".
I should mention the fact that I do not want to "force" anyone to listen to a real center channel. If they prefer to not have one, that is their choice, and I would not wish to interfere with their system. Many people prefer to alter sound in a variety of ways, such as by overemphasizing bass. That is certainly their right (as long as they don't play it loudly into other people's space, as, for example, when one lives in an apartment with acoustically "thin" walls and floors). But it is merely their personal preference, and has no relation to what would be an accurate reproduction of the original sound that the musicians created.
