Was thinking about this earlier.
Here are the categories I was thinking about....
8-Bit (Sega Master System, NES)
16-Bit (SNES, Genesis, Turbo-Graphx)
Arcade Games (Only way I could think to include these)
Disc Gen 1 (Saturn, Playstation, N64)
Disc Gen 2 (Dreamcast, PS2, Gamecube, Xbox)
Next...