Total cop out but if you remove a slice or two, the whole pie looks like the Pac-Man. If you're making the pizza yourself, however, the decoration possibilities are endless (and really fun to prepare with friends or family pre-party). Slap on some mushrooms in the outline of Mario's cap, arrange pepperoni in a Space Invaders pattern, or form a warp pipe entirely out of peppers.
Snack 2: Nachos
Nachos are an easy finger food, especially if you're balancing a drink in one hand. Arrange individual nacho chips in a Triforce pattern for an easy Legend of Zelda association.
Snack 3: Veggie platter
Super-healthy veggies off-set the greasy grossness of pizza and nachos. No natural video game theme emerges from them, sadly, but if you're willing to go the extra mile, cut and arrange the veggies into video game-themed shapes (you could probably pull off a Plants vs. Zombies motif, if you're creative).
Snack 4: Cupcakes
These are a fantastic way to end the night. Bring out some delicious tasty treats, and decorate them to fit what you're doing. Red gel coloring makes fine blood, candy can fill in the details for making eyeballs, brains, or sweeter game related options, like the oft-repeated mushrooms and Mario imagery. Like the pizza, decorations all come down to being creative and finding something that fits your theme.
Entertainment: The key to all the best parties
For a proper Halloween party, we recommend you remove Rock Band and Guitar Hero to the closet, at least until the end of the night. The games tend to kill conversations and render at least four people unable to drink or eat while they hold the instruments. Games like Street Fighter IV (well, any fighting game) also have a habit of dragging a party down, as they glue people to the screen and spark more fights between tipsy gamers. Here are some alternative game-related ideas:
Idea 1: Ambient retro games
Instead of music games, bust out some retro horror games like Splatterhouse, Resident Evil, Eternal Darkness, Silent Hill, etc. The games themselves don't have to be great, but they do have to be entertaining -- or at least lend themselves to pass-and-play so nobody gets stuck babysitting a screen.
Idea 2: Healthy competition