(Putting this in Great Debates because, well, “good guys” is a debatable term.)
I’m not terribly familiar with the Valkyrie plot to kill Hitler. I know it was led by senior Germany Army officers, and that they were unhappy with the way Hitler was managing the war. I can always find common ground with people who want Hitler dead - but what was their plan thereafter? For example, would they have ended the Holocaust? Restored German democracy? Or was it just a failed try at a power-grab by some guys who were somewhat less horrible than Hitler?
My two cents (based on plans that were discussed):
Their main motivation was that Hitler was losing the war and leading Germany towards defeat. They also weren’t real happy about the amount of power the Nazis and the SS had because a lot of that power was taken at their expense. (There were some notable exceptions to the above - people who had opposed Hitler consistently for years, back to when was still apparently successful, for more ideological reasons.)
So the plan was to kill Hitler (that was vital - many potential conspirators refused to commit themselves if Hitler was alive); disband the Nazi and SS leadership or at least reduce their powers as much as possible; set up a new government run by the military and conservative figures (Goering was considered as a possible figurehead Chancellor); and negotiate an end to the war on the best possible terms.
They probably would have ended the genocide against the Jews and other targeted groups. The Nazis and the SS were committed to mass murder but outside of those groups, most people - even those who were anti-semites - were willing to accept less drastic programs.
But democracy was not on the immediate agenda. Neither was territorial restoration - the new government might have been forced to surrender some occupied territory in exchange for peace but they wouldn’t have surrendered any as a matter of general principle and would have held on to as much as possible.