I thought one of the reasons was that the "good" games had a lot of time to develop, often coming out years after the series was on TV. DuckTales for example was a 1987 cartoon. The game came out in 1989. Goonies 2 also had a two year time period, but the first one was pretty awful. Often the games came out after the show had peaked. But times where different back then where you didn't need a game out within 6 months of the show or the same month of the film. Then sometime in the early 90s this changed and a lot of junky franchise game came one after the other.

I don't know about the others out there, but stuff like Atari 2600's ET was made in mere months and it's considered one of the worse games in history. I think a great number of franchise games are forced out in under a year, perhaps in under 6 months. So I like to believe it's development time mostly more so than Japan vs Western developers.