The B-747 is heavier, (833,000 = -200, 870,000 = -400)
and have more power than the C-5.
The -5 may look fatter on the ramp, but if it beats the 747 in anything (With the exception of maintenace cost) I am not aware of it.
The Russians have something bigger again, but hardly a commercial success.
(Like the Spruce Goose, it is still the worlds "biggest" in some category if I am not mistaken....Probably not..
)