NES: no rgb, sucks
Genesis: rgb, nice first 16-bit graphics
SNES: rgb, nicer 16-bit graphics
Saturn: rgb, nice 32-bit graphics
PS1:rgb, nice 32-bit graphics
N64: no rgb, suck-ish
Dreamcast: vga, rules, too few sega ports
PS2: most games 480i only, meh graphics, but the best library.
XBOX: m$, nuff said
Gamecube: pretty ok-ish
XBOX 360: m$, nuff said
PS3: greatness, ps1, 2 and 3 through 1080p hdmi
Wii: 1.5 gamecubes