Well, if we talk about security and driving experience there is no question that the X5 would be on the top of the list and these are the main reasons why we all love it so much. However and unfortunately it is true that from a reliability stand point it does not compare to Japanese SUVs. I am not talking about major mechanic issues but small things like window regulators, AC final stage resistor, etc... On my X in the last 2 years I got 3 Windows regulator replaced, one final stage resistor and few other problems. Nothing big and all covered under the warranty but every time a trip to the garage. I will never understand how comes BMW has not solved this window regulator weakness which has been known for ages.
So when you do a survey about reliability it is no surprise that the X5 does not make the top of the list. A car in that price range should do better IMO.
Having said that, however, I would not swap my X for any other SUV, Japanese or not. Very few SUVs compare to it as far as driving experience is concerned.