It is Deus Ex Human Revolution's fault! It only offers fake post-processing "wash out" Anti Aliasing. But going beyond 3840x2400 was just curiosity how far I can get.
Here is a screen-shot, Tai Yong Medical Penthouse to illustrate (I could have picked any location...).
The setting was 2x MLAA, which is the closest to real AA, all others are post-processing methods. Looks normal you think?
Open this picture and see the for yourself! This is not Anti-Aliased at all. Steps, gaps..
Around the middle, up there the bright area: See how lines are actually broken into pieces. On the right: see how you can make out every ugly step.
Now this it how it started. The first step was reaching 2880x1800, exactly 1.5x. A kind of anti-aliasing "from behind"
Ony my screen it gets rescaled to 1920x1200, and the AA parts look better.
Move the mouse over the image to compare to the original. Click picture for the full 2880x1800 to 1920x1200 downscale.
As a side effect: Smaller HUD which takes less precious screen space:
Next step with is worth mentioning was 3840x2400. That's a quite good result. On the left you can see how lines are actually continuous lines.
You even have more detailed textures which are less jumpy when moving slowly. The ground lines on the right doesn't look like Quake 1 with software rendering.
Move the mouse over the image to compare to the original. Click picture for the full 3840x2400 to 1920x1200 downscale.
The last step which does work as 1920x1200 downscale is 5760x3600. This is what I call Anti Aliasing. Everything sharp and smooth at the same time
That is the resolution I usually play in (if the game can do it and the fps is still OK). Recording a video is jerky and slow tough.
Move the mouse over the image to compare to the original. Click picture for the full 5760x3600 to 1920x1200 downscale.
The HUD is a bit small, but big enough for that game:
Beyond 5760x3600 I cannot make it to work as 1920x1200 downscale any more. When running with 6144x3840 the screen-shots look nice, but on screen it is not 1920x1200 any more.