SNES is 9 or 10 V, 1.2 A, but some are AC and some DC.. I think european ones use DC while US use AC. not sure about the details right now since I don't have one handy, but I know the US SNES can run just fine with a genesis 1 power supply if you modify the connector.
the one i use is the selectable one - i think its 3-12V also its the one with the changeable head - i bought the asortment pack they had and it had all the right heads in it for most of my systems (i had to buy the head for the atari type seperately)
If you buy one of these, be sure to check the label and see if it has a good current rating; many of this type are intended for low-power stuff like portable CD players and such and have low ratings like 400-500mA. Most consoles that have DC input need 1-1.3A.