For the half moon window I would suggest replacing that with rectangular windows the same width as your other windows. For the angled siding areas, I would either go with horizontal siding or a thin brick/thin stone veneer.
Ultimately I think the biggest reason the home looks dated is not these areas, but the monotone greenish gray color scheme. I think a repaint to more vibrant colors (plural) would make a big difference. For example you could paint the main wall areas at dark charcoal gray and the accent areas/window trim areas a cream or off white.
Q