It's seems a strange quote to place in a video game, which tend to be either about acquiring treasure or a shoot 'em up frenzy. The poem opens up, saying:
You told me, I remember, glory, built
On selfish principles, is shame and guilt;
The deeds that men admire as half divine, all.
Stark naught, because corrupt in their design.
This is pretty explicit, and should need no paraphrasing. He is reminding everyone that 'glory' that governs by counting on 'selfish principles' is no glory at all. Given he was writing on the very outset of the industrial revolution in England, and the mobilising of Capitalism as the power in the land, his criticism is apposite. After all, John Ruskin also said that England would have to chose between Capitalism or Christianity. When we look around us today we can see which route was chosen.
The two lines in question occur further along the poem:
To themes more pertinent, if less sublime.
When ministers and ministerial arts;
Patriots, who love good places at their hearts;
When admirals, extoll’d for standing still,
Or doing nothing with a deal of skill;
Generals, who will not conquer when they may,
Firm friends to peace, to pleasure, and good pay;
This again is apposite, when we recall how the military, buttressed by Capitalism, changed war into the industrialised killing fields of World War I and World War II. They could have fought for 'peace' and be firm friends to it. But crazed by militarism they ruined most of Europe. We see this now in hindsight, but William Cowper was able to foresee this from the mid 1700's. A similar sentiment is explored by Kubrick's anti-war film, Paths of Glory, where the French General in charge and the entire military command is shown to be corrupt and in thrall to militarism. In fact, right at the end, at the climax of the film, just after General Mireau is seen crowing with his superior over the murder by firing squad, at his instigation, of three men for "cowardice in the line of duty" and who he descibes as "having died wonderfully" and which we know to have been brave men in the preceding court martial, Colonel Dax, the protagonist of the film, calls General Mireau, "a degenerate, sadistic old man." And that is Kubrick's comment on the then military high command. And could just as well be Cowpers poem, put in a single sentence about the leadership of his day and what he saw coming.