Hasselblad is the best in the same way as Leica. It set a high standard for a medium format system camera, which other brands have tried to emulate with varying success. Some are better at certain things, and some are worse. But a Hasselblad is the benchmark everything else is measured against, just like Leica is the benchmark rangefinder, and Rolleiflex is the benchmark TLR.
I think these iconic cameras were successful because of one thing: balance. They aren't really outstanding for one specific thing, and also have no glaring weaknesses. Any product, especially something as complex as a camera, presents numerous trade-offs for its designers to navigate through. The 500-series is extremely well-balanced. It starts with the 6x6 negative size (the most efficient trade-off between negative size & glass weight & shooting ergonomics) and continues with lenses, repairability, modular design, materials, etc. Most products force you to deal with a wider amplitude between their "highs" and "lows". The Bronica GS-1, which I shared my experiences with just recently, is a prime example of an unbalanced product: brilliant in some ways and "WTF they were thinking?" in others. The same can be said of every other MF camera I own.
People cut them no end of slack and read intent and purpose into the design, mostly because of the halo effect.
The name, the history and the price sets a scene where these heroic cameras can do no wrong.
Of course they are well crafted. They cost an arm and a leg back in the day.
But that doesn’t mean that other cameras aren’t well crafted too, in their own way.
Both the Leica and Hassy are in a sense and in their own way over-designed.
The Hassy is a concept taken from elsewhere and polished by watchmakers to what they saw as perfection.
It still has the frailty and overcomplexity of a watch though. Good ideas don’t often scale. Neither does mindsets.
Leica is the idea of small, light, well crafted and, for what you got, reasonably priced camera, IE the Barnack Leica, “perfected” to probably it’s inversion in the M series.
Both have glaring problems that are brushed off or made into features.
Macro and tele work (and even very wides, where wide angle was supposed to be Leicas forte) is a circus side show with a Leica. You have no way of getting even the faintest visual idea of depth of field unless you turn it into an SLR.
Hasselblad is bigger than a camera that includes two cameras stacked on top of each other (Rolleiflex). Has a pretty dim finder with anything below 2.8 lenses, which are super expensive and scarce outside normal lens territory.
And the party trick of changing magazines turns into a complex rite with lose bits all over the place for what is supposed to be a field camera.
You have twelve frames FFS. How often does changing film become necessary‽ Just finish the film or bring a second body.
No real single point to the above. There are good cameras and there are better. But engineering in industrial design, is as much the art of careful and poetic compromise, and knowing when to stop, as it is the art of convincing people that something is worth it.