Here's a few more 'Evil twins in cartoons/games.' They were featured in the following order of these animated series (and 1 PC game):
In the original He-Man and the Masters of the Universe episode, 'The Shaping Staff,' He-man confronted his evil doppelganger, Faker, in which during their fight, the latter fell into the abyss surrounding Castle Grayskull.
Also, in the lesser known, The New Adventures of He-man episode, 'The Nemesis Within,' He-Man had a tough battle against his duplicate (created by Skeletor) who anticipated and countered his every move.
The Anime series 7 of 7, the original Nana and her 'sisters' had an unfortunate encounter with her evil twin, Jamanana (the 8th Nana), who was cleverly manipulative, and devious.
I can't recall the exact ep. of The Neverending Story animated series, but the evil sorceress Xayide created a copy of Bastian in a scheme to steal the Auryn medallion, and his clone was successful in the deed.
Though not exactly a video game, in the downloadable PC word puzzle game 'Bookworm Adventures,' Lex the Bookworm faces off one of the bosses known as Mirage Xel, who's an evil twin version of him.