The Icelandic sagas known as the Eddas have come down to us in two forms: the Elder Edda and the Prose Edda. The Elder Edda is composed of poems and fragments of poems that connect us to the oral tradition of ancient Norse cultures. The Prose Edda is a compilation and arrangement of many of these poems into mainly prose form. This was accomplished by Snorri Sturleson in the 13th century. While Sturleson's work was translated into English and does contain material about the Volsungs and the Niblungs, the full story did not appear in English until 1870 when a translation was published by Eirikr Magnusson and William Morris.
The Magnusson-Morris translation is mainly written in prose, though some poetry is included. This translation brings the story into modern English and mainly conveys the plot. It has none of the thrilling resonance of Morris's later poetic treatment of the story in Sigurd the Volsung, but its vocabulary is generally limited to words derived from Old English. Consequently, it is able to transport the reader more or less into the ancient North.
Every treatment of "the Great Story of the North" that I have read has it strengths and weaknesses. Preferring one to another is probably a matter of taste, but in each, the remarkable story of the Volsungs, the Niblungs, and the Budlungs shines through and never fails to dazzle. Unlike the heroes of Rome and Greece, the Norse heroes have a tragic nature to them as they face their inevitable defeat. It is how they accept their defeat that makes them heroic.
It is difficult for me to discuss the Lay of the Niblungen without mentioning Tolkien. A good bit has been said about Tolkien's appropriation of names from the Eddas, particularly, Gandalf and Frodo; however, I have not read commentary that has drawn parallels between the life of Sigurd and Aragorn, Brynhild and Arwen, and Gudrun and Eowyn -- parallels that are of much greater interest.
In the Eddas, Sigurd falls in love with Brynhild the valkyrie. Before marrying her he sets off to earn her love and journeys to the house of the Niblungs. There he leads them to greatness, but is enchanted by Gudrun's mother, causing him to fall in love with Gudrun. Similarly, in The Lord of the Rings, Aragorn falls in love with Arwen the elf, but before marrying her, heads off to join the House of Theoden (the Riders of Rohan), also leading them to greatness. Furthermore, just as the Niblungs defend themselves against the Budlungs in a bloody siege in Atli's hall, so too do the Riders of Rohan defend themselves against the forces of Sauruman at Helms Deep. Finally, in a looser parallel, just as Atli, King of the Budlungs, is married to Gudrun of the Niblungs, so too is Grima Wormtongue (Sauruman's lieutenant) seeking to marry Eowyn, daughter of Theoden.
There are, of course, dissimilarities in the story. There is no enchantress in Rohan to cause Aragorn to fall in love with Eowyn as Sigurd fell in love with Gudrun, betraying Brynhild, but the attraction between Aragorn and Eowyn surely threatens to betray Arwen. The most significant dissimilarity lies in the victory of the Riders of Rohan at Helms Deep. Where the Niblungs are defeated by the Budlungs, the Riders of Rohan are saved by what Tolkien describes in an essay as a "eucatastrophe." Out of the blue, Gandalf leads a contingent of Riders to rescue the beseiged, just as the besieged are preparing to end their lives in a paradigmatically Norse fashion, with an honorable and glorious, but completely hopeless attack on the enemy.
Clearly, Tolkien is indebted to the Lay of the Niblungen, but in his hands the story is transformed into one in which hope is triumphant, but while the valor characteristic of the ancient Norse remains undiminished.