According to 2,201 people surveyed, Back to the Future is the film franchise they'd like to see return most. I also found the Star Trek questions and responses interesting.
An astounding 7% of respondents have never seen nor heard of the Star Trek film franchise.
67% of respondents view the franchise "very" or "somewhat" favorably. The rest either don't know or don't like it at all.
And only 32% are "very likely" to see another installment, while 23% are "somewhat likely" to do so. Only 17% say they're "not too likely" to see another Trek film and 21% insist they're "not likely at all."
Overall it's not a perfect survey. (I wouldn't classify Avatar as a franchise with only one movie, for example.) My takeaway was that the more films there are in a series, the less likely a franchise is to attract new moviegoers. Nostalgia is a powerful drug, of course, but over time even that draw wanes.