A380 versus B-747
The A380 has been in production now for about 8 years (through the end of 2014). According to Wikipedia, it has racked up 317 orders. The B-747, at the same point in its lifecycle, had racked up 315 orders. Quite comparable.
However, in the next four years Boeing took in another 239 orders. The way the A380 is going (no new orders this year), it has a lot of catching up to do.
If one looks at the history of orders for the 747, it was quite cyclical - large swings up and down on multi-year timescales. One should be cautious about reading too much into the current A380 slump.
Interestingly, the separation in capacity between a B-747 and its nearest competitor - the DC-10 - was about the same as that between the A380 and its nearest competitor (excluding the 747-8) - the B-777 - a factor 1.5 to 1.6. However, the big strength of the 747 was its range - a factor 1.5 bigger than that of the DC-10, which meant the 747 could operate routes that the DC-10 could not. The A380 has no clear-cut advantage here - the 777 comes in various models that trade range for capacity, and the longest range version outstrips the A380. So I guess one could say that the big weakness of the A380 is its one-size-fits-all characteristic.