Rare is it that I recommend a movie that is not the first in a long franchise series but if you were to watch only one DEATH WISH film #4 is were it's at!
The DVD and Blue Ray market are collapsing because of poor sales(digital theft has created lack of incentive to manufacture new prints) and as a result classic films from the 70's ,80's, and earlier are not being printed to disk or maintained for future generations( and continue to disappear from streaming).
To keep film alive remember ,If you love a film buy it!