Anyone who wants to challenge Apple’s (AAPL) reign as king of the smartphone world has a very big obstacle standing in their way: iPhone customers really, really like their devices. J.D. Power’s latest smartphone satisfaction rankings once again show that the iPhone has the highest customer satisfaction in the industry, as its overall score of 855 out of 1,000 easily bested its rivals and actually represented an increase from a year ago when the iPhone got a score of 839 on J.D. Power’s survey. Other companies that scored well in the J.D. Power survey were Nokia (NOK), which got a total score of 795, and Samsung (005930), which got a total score of 793. Nokia’s high score is particularly notable because the company scored just 702 one year ago, which gave it the second-worst customer satisfaction in the smartphone industry behind than the now-defunct Palm.