There is still much work ahead. "some dude" already warned me about GTA4's unforgiving rendering pipeline and still I wasn't able to get it right from the start.
injectSMAA v1.1 focuses on d3d9 and especially GTA4. It seems to work on my system (see screenshots).
Some people report problems with Skyrim (the screenshots look like confused RGB<->sRGB). I could not reproduce the bug on my (GeForce GTX 560 Ti) system. Maybe some modifications to SMAA.fx can help those people (like changing "SRGBTexture = true;" <-> "SRGBTexture = false;" or "SRGBWriteEnable = true;" <-> "SRGBWriteEnable = false;") but is not recommended.
For more information visit the "injectSMAA" page.