To me, the Full Frame edition of BTTF looks better than every other DVD edition that you can find. The quality is amazing, there's less MPEG compression artifacts than the widescreen versions. The colors as well look fantastic.
Full Frame DVD:
http://i681.photobucket.com/albums/vv176/milkytrv900/vlcsnap-2013-01-04-19h49m30s201_zps02faa95c.png
1.85:1 Blu-Ray:
http://i681.photobucket.com/albums/vv176/milkytrv900/vlcsnap-2013-01-04-19h50m41s244_zpsaa0fb64e.png