These things are difficult to answer, as there are so many choices.
Then again, you could always go eclectic. I mean, who would not want to hear "Spiders and Snakes" by Jim Stafford in 5.1!
Now that you mention it, NOT the first remix that came to mind, but I do wish there were compilations of nonsense like that in 5.1 to perk up this snowy Feb afternoon.
Given a choice...one act I'd like to hear is Vangelis, the Oscar winning film composer, former member of the dreadful Aphrodite's Child, but master musician and technician behind so many interesting and influential albums like ALBEDO 0.39, HEAVEN AND HELL, SPIRAL, various soundtracks, etc. His music would be wonderful for 5.1.
Brian Eno's, too. And Roxy Music: the kind of music that is often intricate enough to make a 5.1 mix a whole new experience. Tangerine Dream: goes without saying. Some New Age music would work well, and Ray Lynch would be wonderful in 5.1, as would Enya (whose music desperately needs that expansive potential that many sound systems--and her own mixes--don't allow). Yes? Of course! Prog rock is a sensible choice for 5.1, as would be the '80s Moody Blues.
For older acts, I'd be more selective. The early Beatles and Stones would be useless in 5.1, and some of it's no big deal in stereo. I can't think of many '60s acts whose catalogs would justify such a program. Another matter once you get into the '70s, of course: Led Zeppelin would be well served, and to a degree, Neil Young, of course, whose championing of optimum sound is laudable even while his output could still use some serious tweaking and organization.
Then there is Miles Davis, who has so many great Columbia albums that the handful we do have in MC just whets the appetite for more. Heaven for me would be a serious box set gathering together all those '60s albums from SKETCHES through IN A SILENT WAY; it just seems so logical, and even the mediocre Miles would be a treat.
But I'd really like to see more compilations of varied material. When I think of all the music you never hear on the radio--even with Sirius satellite, there seems to be so much missing--that random various artists collections of material of whatever variable quality, would be a kick. But then I'm easily bored, and constantly in need of stimulation in my dotage...
ED