I'll just argue that the perfect fifth is.
There was a study that Matt posted to rebut the idea of consonance and dissonance that showed some tribe who hasn't developed harmonic system and have them rate all intervals of western system in terms of whether they like the intervals and they found that there wasn't statistical significant difference in the intervals.
Even ignoring the methodological flaws (people politely saying they like everything, judging intervals in the absence of context of music, people may like all the intervals but if you frame the question which you find represents order/disorder or get people to rank the intervals from the most ordered to disordered would get more accurate results rather than simple yes/no answer)
The perfect fifth came out as the most popular interval even if it didn't reach levels of statistical significance. Maybe that's not a coincidence?