Beowulf is an Anglo Saxon hero that has inspired many similar heroes. Being an Anglo Saxon hero means that Beowulf is immediately three things: a young, white, male. That's really no different than current pop culture heroes (Luke Skywalker, Captain America, Thor, Green Lantern, Wolverine, Jason Bourne, James Bond, Harry Potter, etc.).
In addition to being a young white male, Beowulf is a "manly man" with really big muscles (he did rip off Grendel's arms). He is a mighty warrior, and people recognize that right away.
Nor have I seen
A mightier man-at-arms on this earth
Than the one standing here: unless I am mistaken,
He is truly noble. This is no mere
Hanger-on in a hero’s armour.
Beowulf is also brave. He has to be in order to willingly face a man eating monster who is supposedly descended from the line of Cain.
On top of all of Beowulf's awesomeness is his humility. People like him, because he's a nice guy too. He's not stuck on himself. He is not a warrior for personal glory. He's a warrior because he genuinely wants to help people.
"The mildest of men and the gentlest, kindest to his people, . . ."