Overwatch is my personal game of the year. It's a game that takes the best mechanics of old-school first person shooters like Quake and Team Fortress and pairs them with mechanics from other genres like MOBA's and fighting games. It's a game that doesn't take itself too seriously, yet makes for some of the most exciting, team based, competitive multiplayer ever made.
Blizzard, the games developer, has done a fantastic job of supporting the game post launch. In a lot of modern games you have to buy new content. In Overwatch, all of the new playable content is free. The developers have also created new content based on different times of year. There have been events centered around The Olympics and Halloween already this year. By keeping the game fresh with free content, and continuing to balance the game they have built a very large and loyal fanbase.
Overwatch is the kind of game that I recommend to parents when they ask me what game they should buy for their children for Christmas. It's a fun, fast paced shooter without the gore and ultra-realistic tone of modern military sims, and it encourages players to act as a team. You also don't have to worry about buying multiple DLC packs just to make sure that your kid can play with his/her friends. As long as you have an internet connection, this is absolutely the game to buy for kids this Christmas.