I've been following this discussion and I'm still trying to figure out exactly why Seabreeze, you chose this particular curiosity of the solar system as significant from others?
As others here have pointed out, the solar system is full of quirks and notable unique differences. The moon just happens to be the right size and distance so that when viewed from the earth, the moon and the sun appear to be about the same size. That's it.
The moon is only the fifth largest moon in the solar system. Something like three of Jupiter's moons are bigger than the planet Mercury and would be considered planets in their own right if they weren't moons. The four big moons of Jupiter are all unique and interesting.