There were once a great deal of 747 flights to Denver... 1-2 years ago, with United (to SEA, SFO, LAX, ORD, and IAD at various times), British Airways (LGW), and Korean Air (SFO-SEL). There are currently none.
Korean Air has left Denver
British Airways has switched to the B777-200ER
United currently only flies B767-300 and B777-200 jumbos to Denver, these along with double B757-200 flights replaced the B747-400s.