Dead Space 2 doesn't support anti-aliasing in the traditional sense as it's a 100% differed renderer, you "might" get away with forcing supersampling but it may well break and or not provide the desired result. You can't force multisampling because the forced multisampler is a forward render system and the point at which it's forced into the pipeline with a differed render there's nothing to sample yet
Best thing to do with this game is use MLAA from your control panel or use an SMAA or FXAA injector
Since crimson I haven't been able to apply AA in the driver whether it's enhance or override, it's very annoying as my friends with Nvidia have no issue overriding their game (IL-2 BOS) for instance or DCS 1.5 or 2.1 no game works.
For that reason I also gave the example of the rainbow, I also have problems with graphics.
Edit: I did not say rainbow example , sorry
Here are some photos
And my configuration is the same as Pro players in youtube That use this configuration and they look very well, it may be that the resolution is also causing this? 1366x768 is my resolution