I don't know if there are newer versions of xnes out, but the version that I used (about 3 months ago) really sucked.
Get FCEUltra. It works perfectly with *every* single NES game that I've tried. Plus it's got save states, resizeable screen, SRAM saves and about every other feature that you could want out of an emulator. Beta 2 is the latest AFAIK.