Why is 2 Channel better than multi-channel?

I'm not sure what you want to know. Do you want to know why a multi channel amp, with the same specs as a 2 channel, sound different when listening to a just a 2 channel amp on its own?
I've noticed that a mulit channel amp does a very poor job on 2 channel. That's why I use the 2 plus 3 amp set up.
As for music in surrond in general ( if that's your question) Is just sounds bad. My thoughts.

"Do you want to know why a multi channel amp, with the same specs as a 2 channel, sound different when listening to a just a 2 channel amp on its own?"

Yes I'd be very interested why.

"As for music in surrond in general ( if that's your question) Is just sounds bad."

The people a few posts up disagree with you, why does music in surround sound universally bad or are you just saying it sounds bad on your system?

Many recording has been optimized for 2 channel.
I have 5.1 set up with Nautilus 801 and Levison gear.
On some recording such as 1812 SACD, I do find the multi-channel provides deeper soundstage however, it is not as forward or details perhaps due to the loss of resolution on multichannel format. I heard that the two channels is 24bit/192KHz but multi channel is 24bit/96KHz.

Asin,

"it is not as forward or details perhaps due to the loss of resolution on multichannel format."

Actually your brain cannot focus as well on the "little" details that are really unimportant in the end because you are immerssed in such a large soundfield. The resolution of the SACD is equal on each channel whether its 2 or 4 or 5 channels being played back. 2 channel is effectively removing 2/3rds of the ambiant field, it is actually lower resolution.

Why digital sounds so thin in two channels has everything to do with this over focused truncated soundstage and lack of an ambiant field. So for better or worse, your perception is a common one but not for the reasons you attribute it too.

There is no real decoding, except for system adjustment like distance your seated from the speakers.

"24bit/192KHz but multi channel is 24bit/96KHz" may change the sound but not the resolution.

Cinematic - I think the main reason why 2channels just don't get MC is that have a tough time grasping the concept to 5 speakers working as one, just as two can work as one. Or am I talking newbie jibberish again?

I can guarentee if the MC system was setup properly, they would understand.

Agreed?