The early 3D systems aged the worst with the N64 having a slight advantage in some areas.
The Dreamcast, PS2, Xbox, and Gamecube have aged decently, but the SD resolution holds them back. The Gamecube, Dreamcast and PS2 emulators have shown that the games can still hold up well if viewed in HD. Still waiting for an Xbox emulator.
The NES, Genesis and SNES have all held up very well thanks to their simple classic graphics. They are all still stuck in SD, but the SNES and Genesis have some absolutely stunning games thanks to some killer art directions. The SNES has a few extra graphical tricks up it's sleeve while the Genesis has stuff like the Sega CD and 32X that help it break beyond 16bit limitations.
I'd say the SNES and Genesis hold up the best.
