Schmidt for sure. Matthews was certainly better.
Boggs and Beltre had similar value, with Beltre being higher. Boggs walked more and has a clear lead in OBP. Beltre had far more power though, he hit 350 more home runs than Boggs and has a clear lead in slugging. Boggs has the advantage on offense, but Beltre is far superior defensively and and on the base oaths.
I guess Chipper, Robinson, and Brett were better if you don't care about defense.