The gender of the lead character(s) doesn’t have anything to do with whether something is shoujo or shounen. The real determining factor is the magazine in which the series ran in Japan. In the case of Game x Rush, this magazine was Hana to Yume, the same shoujo magazine that hosted Fruits Basket.

Some other shoujo series with male leads include Banana Fish and Here is Greenwood. Examples of a shounen series starring female characters include Claymore and Aria.

Hope this helps!