I just have had a look at the GamesCard. The javascript is still used. So it must be a simple syntax error.
Best is to add a test line in games_bigcover.htm. Open that file and search for following line:
<script type=text/javascript>var extb = '_GAME_GENRE_'</script>
Now add:
<script type=text/javascript>alert(extb)/script>
This new line shows you the correct spelling of your genre which you have to add in the code below.
Also have a look if there is no typo in the picture name and the format is correct, too.
} else if(a == "Instant Action - First Person Shooter") {
document.write('<img border="0" src="GamesCards/Genre/InstantAction.png" width="48" height="48">');
} else {
document.write('<img border="0" src="GamesCards/Genre/unassigned.png" width="48" height="48">');
}
}