Active Games
Typical active "girl" games that can also be mastered by boys are jump rope, hand games, hopscotch, hula hoops and tether ball. Girl games tend to involve more social interaction, while boy games involve more physical challenges. Gymnastics is a fairly girl-specific activity. Gymnastics is an excellent activity for boys to participate in because it requires strength, endurance and aerobic exercise. Dance and ice skating favor the girls over the boys, but both take dexterity that boys will find satisfying.
Creative Games
Drama games, dress up, tea parties, playing house and playing dolls are predominately girl games. Quiet, hands-on creative games involving art, painting and sculpture are geared toward girls. Boys can be encouraged to play dolls and house, especially if the game is geared more toward their interests--if they can help build the house for the game, for example, or play the dad coming home from work on his bicycle. Boys also enjoy simple artistic endeavors, like making friendship bracelets.
Online
There are online game sites geared toward girls that have sections for boys who might be interested. There are cooking sites that encourage boys to be as involved as girls. Cooking is a task that boys can master easily because they are given a set of rules and asked to complete the rules (or recipe) in a specific and short amount of time. This is perfect for the boy brain's need for fairly quick satisfaction.
There are doll dress-up sites that have games geared toward boys: the boys get to pick out male characters they might want to be. They get boy-specific activities, like picking out cars, pokemon characters, trendy outfits and hip-hop styles.