few months ago I played a quick game at
http://armorgames.com/play/2409/mastermind-world-conqueror
and seeing evil genius I understud where they find the inspiration :)
only the game were a bit too shallow, not worth a replay.
i really like to know what evil genius had more that that quick game, because i really like the idea but despise spending 10$ in something not worth more than one quick game...
there are certainly many things more than a little flash game :)

Evil Genius definitely has a lot more style and depth, and it holds my attention more consistently. The gameplay focuses much more on building your base and setting up traps, rather than carrying out evil missions - if you've ever played Dungeon Keeper, it's very similar to that in many ways. Most of your focus will be on building your lair and training / living spaces for your minions, and defending your base from the occasional wave of armed do-gooders with things like fire pit traps and laser tripwires.
You'll certainly get more replay value out of it than Mastermind, and in my opinion it's definitely worth $10.