I'm not sure if you have a particular film in mind, but it's not uncommon for critically acclaimed films to be box office bombs. If you're talking about non-contemporary films, it's also worth considering that different films have become cult classics or fallen out of favor. Plus, they way RT calculates each score is different. There's lots of reasons why the percentage of critics who give a movie a "thumbs up" might be different from the viewers' average score on a scale of 1-100.
>>dfxm12+(OP)
I specifically said they use different metrics. The different score isn't the problem, it's the size of the schism.
40 million people not paid to review movies seem to hate this movie; but the 100 people who love it are both A) paid to watch it and B) seem to entirely fit the vast minority of viewers who like it.