Watching my kids play with their computers, I'm absolutely astounded by how much things have changed in the 30 years or so that PCs have been a part of my life.
My kids like to play games. With me as their dad that's probably no surprise, but it might interest you that the vast majority of the time they spend gaming on their computers is spent online -- typically in community sites specifically oriented to hosting games kids can play.
Compare this to 30 years ago, when I, as a 7 year old, was introduced to PCs through my "big brother" Ron's TRS-80 Model 1. If we wanted software, we had to program it ourselves and write it out to a cassette data recorder, at least until Radio Shack realized there was a cottage industry in this whole software thing.
Fast forward a few years to my first Macintosh -- a "Fat Mac" circa 1985 -- and the Apple 1200 baud modem I got from a friend, trading my entire TI-99/4A rig for it (a deal that I still say I got the upper hand in). I started tooling around on bulletin board systems and discovered you could download software from them, too. Though some of it was illegitimate, much of it was something I'd come to learn was "shareware," which meant that if I liked it, I was obliged to send the author a check (or sometimes just a post card, or something, to let him know that I'd tried it).
But for the most part, to satisfy my gaming jones, I'd buy software. El Gato, for example, the submarine simulator, or Dark Castle, or Deja Vu. Games were on floppy, then, post-Myst, CD-ROM, then, more recently, on DVD.
Now, however, monolithic games on disc are becoming a bit of an afterthought for my kids, as they find richer and richer gaming experiences online.
Sure, really intricate games are still the almost-exclusive domain of CDs and DVDs. But with digital distribution systems like Steam in full force on the PC, and burgeoning equivalents like Gamerhood, Deliver2Mac and others, it doesn't seem long from now that game discs all together will be a forgotten relic.