I played perhaps 1000 hours on starcraft 1 or 100 hours on a GTA a long time ago. That's the kind of player I used to be.
I'm now 34 years old, and I'm good with around 15 hours of playtime (including a few retries on fails) for a good game.
4 hours is still really too short for me at this point, both in term of value (short games are not so much inexpensive) and pleasure. 4 hours dont give me any sense of progression in term of gameplay, story, art, I feel that's a waste of time. For most games 30 hours is way too long, I would got bored or leave in the middle because I don't have time. IMO only a very few games could be soooo good I could play them for such a long time.
For megadrive game length I think it was a totally different concept without save and as a not so skilled kid for whom everything was just fresh and good. I was not even aware games were so short. I was just thinking about how much I played, and enjoyed the game for 30 to 50 hours, sometimes for months. Back to the day, I didn't care trying again and again doing the exact same level with an extremely limited set of actions (sonic 1 use mostly left-right-jump buttons). Now even with 100 times more play value I could not stand playing so much.
