Angel evolution.

In the third and fourth games, they heavily relied on the Christian image of an archangel.

I doubt it (unless you're talking about the ones in the third game, that's true). I mean, there's not much else to draw inspiration from, and I'll say something unexpected, but there aren't any other images of angels besides the Christian one, really. But it doesn't seem to me that the archangels in the third game and the angels in the fourth game are closer to that image than their counterparts in other parts, as the fifth game and CoH surpass them in this regard.