It's not that games today are good, it's that they're addiction factories. They're designed to keep giving you psychological rewards to get you to keep playing. It's the reason why every game keeps getting level systems and loot drops even when they don't help keep the game interesting - they're just skinner boxes that are training you to enjoy the experience.

That's not to say older games didn't also use them at times, but they are a whole lot more prevalent in modern AAA productions.

Also as others have mentioned, older games are generally not designed to take up as much time as modern games.