By increasing the internal resolution (x4), the filter becomes unnoticeable. And by using scripts to exactly reduce the window size by 1/2 (320x240), and centering it within a 256x224 screen resolution, the result is pretty much 1:1 what it would look like running from a NES.

One of the cool thing I've been running on my "PC on CRT-TV setup" is Mega Man 9 (and 10), properly scaled to CRT-TV resolutions.
The Wii version outputs natively to 640x480 and has a hardcoded bilinear filter that softens/blurs everything.
BUT...