When I was still a PC gamer, pretty much all that's been mentioned already. (except for the onslaught of cheap digital games, that was later, it just stresses me out how many unplayed games I have access to now lol)
But I'll add the ability to cheat. From backing up save games that are supposed to reset on death, to editing the save games giving you more money/resources, to active cheats that alter the game in progress. As long as its not online I don't see an issue with it. Playing billiards with cars in NFS Most wanted by instantly changing the speed of the car was actually more fun than the game itself!
Lan play! When I was still playing mostly on PC you only needed one physical copy to play co-op or vs in lan. One copy of Unreal tournament worked with 4 networked pcs, IL-2 Sturmovik, NFS Porsche Unleashed against each other by simply putting the disc in the other machine when it asked for it. As long as all the pcs had the same windows version, lan play was easy and tons of fun.
Plus I still miss the days when my wife and I played Everquest and WoW together side by side. No time for that nowadays nor can I sit behind a pc for that long either anymore. But those were great times.