Super Mario games and other in under an hour? You'd have to take every shortcut available and do a speed run to manage that. Just because Duktales was TOO FUCKING SHORT doesn't mean all platform games from that era were.
Uh, yeah they were. The idea is that the games were difficult so you'd never beat them on your first try (and that's true of Duck Tales as well), but on your winning run you'd easily clear them within an hour. Super Mario Bros. 3 and a few others like Blaster Master or Street Fighter 2010 were a bit longer I'll give you that, but pretty much everything else was around an hour or so.
As for Super Mario Bros., it's pretty easy to clear that game within 10 minutes if you take shortcuts. Without shortcuts we're looking at 32 levels that are no more than a minute or two long. Yeah, an hour is reasonable.