I'm 40 and still love gaming. I have been playing games since the Atari 2600 but I loved arcade games when I was a kid because 30 years ago the arcade games were far superior to what you can play at home. I have kids and they are all games now. I hope I didn't ruin their lives by wanting to be inside most of the time.
I would say racing games are my ultimate favorite. RPG's are number 2 in my book. Shooting games are third. It took me a while to convert from mouse and keyboard shooters to the dual joysticks. This took some time and I almost gave up convinced that I would never be good at console shooters but eventially I broke through and now enjoy the hell out of shooting games on a console.