Most games I play average 30-40 hours which is what I've always considered standard so idk about that... There's also really not much to encourage replay value in older games aside from if you like them or not.
Replay value was a huge challenge for devs back in the day, so the general solution was either to make them extremely long, or hard as ***. Usually a mix of the two. But because the demo for video games has expanded so significantly over the years, so have the demands and standards, which is why many of us feel a bit alienated by the level of hand holding and casual appeal rather than well planned, budgeted, and produced triple-A titles.
But I'm impressed that 30-40 is your standard by today's means. Even more impressed you're not disappointed again and again by what comes out today. Then again, you could be very critical on your purchases, and be a smart buyer, knowing what you're getting before you dish out that $60.
Games these days have as little as 4 hours of gameplay content, and as much as maybe 20ish, depending heavily on genres and DLC.