I think one of the best innovations in gaming throughout the years is cooperative gaming. Starting back with Contra for the NES, and recently, Halo for the Xbox, cooperative gaming is just plain fun.
X-men Legends is another fun one, and Star Wars Lego’s. Co-op games are just fun to sit down with friends and play together, you can actually be a “team” and play together. Games like X-men Legends, four people can play together, great times.