It depends on the kind of trading you are in to...
I am a person who these days makes his living (85% of it anyway) off position trading, and probably the best game for this is Civilization.
Basically you make a series of moves and the result is uncertain for a while (except for the informational stop outs, where you get relatively fast feedback)... but if you make the right moves consistently well then a positive kind of result WILL be on its way (its just gonna take some time to reap the massive fruits of your endeavors)...
If you are a swing trader (15% of my trades), perhaps some kind of lower complexity, quicker feedback strategy game would be of use... the game should also be lower stakes than Civilization to reflect the less fat tail nature of swing trading relative to position trading...
For rapidfire intraday players (I have grown out of this high effort to reward ratio game and can't remember the last time I intentionally pulled up an intraday chart), the new Wii sports games may fit the bill:
In a nutshell, immediate feedback provided and fast reactions needed... little time to think deeply... and also the kind of game (be it intraday trading or Nintendo Wii) that appeals to the younger ones
There are as many categories of games that there are categories of trading, imho...