Because the ones that we hear about are the ones that are good enough to have even made it out of Japan. If a game was bad, it wouldn't be localized to an English-speaking audience, and we wouldn't even know it exists.
It's the same sort of thinking as asking why (insert media here) was better in the past. The answer is simple - good songs, games, movies, etc. tend to be more memorable, and so we remember the good ones and forget the bad ones. To put it briefly, there's survivorship bias.