Generally, I prefer to enjoy the source in the number of channels in which it was recorded.
I like my two channel music in two channel stereo. I prefer movies in whichever mode it was recorded in, be it 5.1. 2.1 or even 1.0. The decoder in my HT receiver in the living room handles that for me.
Note that this post refers to movies only. For the normal day-to day television programs, I don't bother with either. I use the TV speakers.
Now, in the man cave/office/gym in the cellar it's a different story. I run an ancient Marantz 2270, a pair of JBL L-26's and a host of modern sources (DVD, CD, VHA-Hi Fi nd a cassette deck) with a 27" Toshiba on the side.
Now, this makes a grand meeting place for the guys when we all get together and I make no apologies when putting on a DVD and having the sound in 2.0,which is all that poor old dinosaur is capable of. We pour the Cardinal Mendoza and enjoy whatever is on the screen.
IOW, movies still sound PFG in two channel but, given my druthers, I'd prefer a decent full MC system.
But, given the choice between a good two channel system or one of these $68 Coby HTIB systems from WalFart, I'll go for the good two channel any day.