The problem with MSAA is that it only handles aliasing from geometry edges. It's pretty much useless against shader aliasing, which became a massive problem after normal mapping and HDR lighting became standard in the PS3 era.
This is only a problem if you naively undersample the normal maps in your fragment shader. No AA algorithm can can generate a high quality result from undersampled lighting calculations.
MSAA also doesn't require you to have only one color sample for each pixel but this can be varied per draw call (at least for desktop GPUs) - effectively allowing you to supersample some objects when needed.
