This paragrahps, taken from the wikipedia entry on ‘evil genius’ sums up why I love the site:
The evil genius is different from the mad scientist, in that the mad scientist tends to be amoral, rather than evil. An Evil Genius is generally a clever schemer, while the Mad Scientist typically pursues scientific knowledge with no regard for the consequences. A mad scientist might create an army of zombies, just to see if it is possible, but an evil genius would have a diabolical use for this army, and a plan to escape the town without being killed.
Now try and find that explanation in any other encyclopedia.