Wow Kirby I am surprised! The one in a 100 thread, that actually makes sense and is not all about spam. 
OT: I think they were so well rated just because on how the indusrtry used to work... some are criticised more today, some less. Doesn't mean that Super Mario Bros. 3 is any less fun if you play it today, but if you think about it, with all the competition in today's market, games like SuperMario 64 for instance wouldn't be appreciated that well because they are in steady competition to at least 10 other games, that might be as good or even better.
The thing is that all the 'Nintendo classics' were pretty much trendsetters in terms of art design and control and thus are remembered as some of the best games.
Also, as you mentioned before, back then competition was not as cruel as it is today. In the NES/SNES era there were almost no games like Mario or Zelda that could compete quality wise.
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