MUC does indeed have some of the longest runways in Europe (not couting millitary) but they are 'only' 4000m x 60m (which is 13,123ft by 197ft) sounds a lot, but the elevation is 1497 ft. It will be perfectly enough for any version of the A380 to liftoff.
The 747 at 0ft and (I think +15°C, no winds) needs 10,000 ft of runway (3048m).
DEN is building a 16,000 which is the longest CIVIL runway afaik.
I think the longest ACTIVE runway is one of Edwards AFB's 30 runways, it is somewhere in the high 20k ft or even 30k ft long.
The required takeoff length depends on a HUGE number of factors which include: Mass at takeoff, elevation of runway, current outside air temperature, SLOPE of the runway (quite important if high), etc