I guess we'll start with Hrothgar here, as his achievements were responsible for the position he held within his society. As a people, the most important thing that Hrothgar represented was good leadership. The second, building a great hall to protect his people, and the third..... he was faithful to those who followed and showed him loyalty.
Beowulf, on the other hand, was eager for fame and easily extolled his own virtues. He cites how he has destroyed a tribe of giants, fought and defeated sea monsters at night, and protected his own homeland. The people see heroism in Beowulf and value his assistance.