These are beginner-level papercraft projects. Not at all hard to make. A suggestion, though:
When I made mine, I really wanted them to last, so I did some extra stuff and things. You're definitely going to want to use cardstock, anyway, (which is easy to get at places like Walmart in the stationary section), but if you'd like to give these as gifts, you're going to want to shore them up even more. And by the time you're done, people are going to be surprised they're actually made of paper. One tip:
Go to the scrapbook section anywhere (Michael's, JoAnn's, Walmart) and grab some black cardstock. You can buy it by the sheet in a lot of places, for, like 70 cents a sheet, and if you get the 12x12 size, you won't need more than....I'd go with 5 sheets, because it's always good to have extra in case you make mistakes. After you've printed out the patterns for the arcade games, cut them out, and score the lines where you'll be making the folds. Once you've done this, glue black cardstock to the backs of each section. The scoring you just did will act as a guide for this. You want to do it this way so that when you do the folding, it won't make the glue pop off and separate the black cardstock from the pattern. It's definitely a fiddly process, but there are two reasons why it's necessary:
If you just cut one of these out and build it straight out, you'll see that once it's done, the recessed area around the game screen is all white, which, of course, ends up looking completely wrong. The black cardstock will remedy that problem. The other reason it's necessary is that having the paper doubled up will make the model considerably more stiff and strong. And for gift-giving purposes, you want it to be as durable as possible.
If you've got ink your printer, this is a very economical gift. All you have to buy is glue sticks and cardstock. Here are the links to the patterns. I couldn't find the Ms Pac-Man or Galaga ones pictured above (I made mine a few years ago), but the ones at the link are just as good: