Jnes was my first NES emulator, and I've enjoyed using it very much these years! But recently I've acquired a CRT monitor, and after some research and tweaking, I've managed to make it display 240p. It's a joy playing retro games in their native resolution, pixel-perfect and scanlines. But sadly Jnes can't display that resolution very well. Besides not having it in the fullscreen resolution drop down list (I managed to force it through the .ini), there seems to be a forced bilinear filter. Using either default or nearest neighbour, will make the picture blurry, even at a resolution like 640x480. I know that's more for modern displays, because the higher the resolution, the sharper it looks, and the pixels won't be "out of place", but I think "native" (I know it's never truly that way for any emulator) should be supported. I made a small comparison with SMB 3, running at 1280x240 ("super" resolution) on Jnes and another emulator, with default settings (no palettes, and correct 4:3 aspect ratio):
Mednafen, NES core (not Retroarch, Mednafen with Mednaffe GUI, easier to configure 240p):
Notice how blurry the Jnes pics look. I would love an option to disable simple filtering (I actually don't know if it's linear or bilinear), so that true 240p wouldn't look like that. I like Jnes because it's practically pick up and play. Other NES emulators I've used, obligatorily need many configurations to set up (not that I completely dislike it), but when I knew nothing about emulation, Jnes was there, and now I can't let it go XD.