This is a very interesting question that you raise. I have B&W DM302s for my front L & R and the mighty B&W CC3 for the front center. When I am in a surround mode (DTS or Dolby) the integration of the 3 front speakers is wonderful "depending" upon the asset being viewed. There are some TV broadcasts on HD that are 5.1. I do notice that on some of them, the dialog comes primarily from the center and music and sound effects spans all 3. So the answer from me is... it depends.. upon the audio being played and how your AVR directs and separates the audio. In some Stereo modes I do notice that the center channel is dead, again depending upon the audio being played. This is and has been a puzzlement.
Many different preferences. There are those that say it is great, there are those that say stereo is better with a phantom center, etc. In the end it is all a matter of preference and which lay out your ears prefer. Listen well and choose.
As pointed out, it really is more of a factor in how it was recorded and transmitted, than the receiver capabilities. A well mixed 5.1 can create an incredible sound stage with a much wider sweet spot for listeners not sitting on axis with the left and right channel. 2 channel can sound just as good but is unable to accomodate more than one listener optimally (this is the home theater section, isn't it?).
I have a fairly decent two channel system that I have listened to for years and I would never give it up but the more I listen to 5.1, the more I have grown to appreciate what more speakers can do to more accurately recreate sound over a larger area.
Just having the center channel that is performing better due to its usually better placement in relation to the walls can be all the reason you need to learn to appreciate multi channel music and its benefits.
And, as pointed out earlier, you can always use "direct mode" or "pure direct mode" with little effort.