digi2 - The major difference being the B747 is an American aircraft, widely bought by USA carriers and the A380 isn't!;)

That said, many USA airports, JFK comes to mind, never did much to their taxiways etc. to accommodate the B747 either!

There might well be some competition for the Boeing 747-400ERF from the proposed 747-400 pax to freighter conversion by Cargo Conversions LLC due in around two years. They are using the same door and most of the same engineering as for the 747-200 pax to freighter conversion and are not going to be removing the upper deck beams after discussions with operators. With the recent reduction in values of the earliest 747-400's I imagine this is becoming more viable every day.