If you're buying for your kid as well as you then start with Lego games. They're simple adventure puzzle games and follow all our favorite movies or comics (Star Wars, Indiana Jones, Harry Potter, Jurassic Park, Marvel, Batman, etc) pretty faithfully while adding a lot of humor that the adults understand having seen the movies or comics many times. Great simple fun to play with your kid and all are pretty cheap.
For you, there is a new Ghost Recon. Wildlands. Pretty great game. You can get the Master Chief collection for cheap that has Halo 1-4.
You can buy the physical disc still if you want. However, once you download a game and not have to get up from the couch to change to another one, you won't want physical copies again. There are a couple RPGs available that play like older style games but honestly there are so many games to choose from you'll have to see what piques your interest.
Have fun man.