As rincewind said earlier, a higher resolution will help make jaggies look better. Of course Anti-aliasing helps, but that is usually a huge performance hit.
a lot of the time, the HUD and text scale with the resolution, so a higher resolution will get you smaller clutter on the screen.
Everything looks sharper because there's more space to define details.
Take this for example: Taking a picture with a 1Megapixel camera and taking a picture with a 5 megapixel camera. Then blow them both up into a 10ft x 10ft poster. The 5 megapixel picture is going to look clearer of course