Old games are generally all about the challenge. Back then, nothing really had things that are now considered "standard" to video games. Shiny graphics, voice acting, plot, mechanics, and interactivity were nonexistent. So, the success of video games was achieved through the challenge and reward system. Game A is known for being hard, players don http://files.sharenator.com/challenge_accepted_RE_Dragkyre_Vs_Nightmare_Our_minecraft_Challenge-s325x265-177836.png, and you have a lot of bragging points if you make it to the end. It was all about scoreboards, really.
As time progresses, gaming becomes less about your performance and more about experience. Cue the modern gamer. Gaming evolves into much deeper experiences complete with everything I listed above. Nowadays, people can care less about doing everything perfectly and more about the entertainment that comes with it. Games that punish you aren't considered all that fun anymore (not to say people enjoy games that baby you either, there must be
some balance

) and a game's quality can be judged on its delivery instead of the "You Win" text at the end.
Video games today are slowly but surely becoming more like interactive movies. Back then, I don't think anyone would believe you if you put forth the possibility of "Drama" or "Psychological Thriller" as a genre of video game. Games today like Heavy Rain prove that video games can be great for a variety of aspects. Story is now important, because no one wants to play a video game that doesn't make sense (unless it's supposed to be that way by design). And by putting emphasis on those aspects, not inhibiting players from progression, they can feel free to enjoy them more without having to work for it (just as you don't need to acquire more audience points or something to watch the second half of a movie". Games become shorter, but that's fine because less people are likely to actually complete longer games.
Multiplayer has also helped advance the industry by creating games that are essentially like competitive sports. It's no longer necessary to create a game with X number of hours in the main story, but the multiplayer included can provide hours upon hours of additional time spent playing. This is possible because a challenge is always present and the experience is different every time. Same applies for MMOs, which are driven entirely by the concept of multiplayer. If you want to be a hardcoe gamer today, multiplayer is usually a requirement.
Fortunately for all of us, nerd rage appears to be slowly going away...