The Mac has more pixels on a larger area(2880 by 1800, 15.6", 220 ppi) than the Samsung (2560 by 1440, 13"?, 220 ppi) so the pixel density is about the same. Since this isn't a shipping product, it might be a bit premature to say that Samsung came up with the first retina ultrabook. Battery life might be problem (small battery, huge power demand from the display). Still, why wouldn't PC makers also use high density displays in some models? It's not magic, just engineering.
No, it's only magic when Apple does it!