Quality of video codecs is not something I dwell much time on but I throughly enjoyed ExtremeTech's excellent comparison of video codecs.  They compared the quality and performance of four codecs: DivX5, WMV9, Quicktime, and MPEG-4.  DivX5 and WMV9 came out on top although I thought WMV9 was clearly superior to DivX5 except in encoding speed.  Two surprises for me.  I thought Quicktime was better than the comparison showed and didn't know MPEG-4 sucked that badly.  Phew!