I really don't think it is a fair comparison. But I may be prejudiced because I have never found Luthien anything like as interesting as Galadriel. And Beren never really appealed - especially as I blame him for FInrod the beloved's death
...
We don't really see Galadriel try her power when the Eldar were at their peak in the elder days and by the time of LOTR, Galadriel had borne a child which depleted the strength of Elf women. Nevertheless she is undoubtedly the most inherently powerful of the ELdar remaining with or without the ring and I would say at least's Gandalf's equal before his encounter with the Balrog. With the ring she has the strength to repel all but Sauron himself and she is able to cast down Dol Guldur even after the RIng is destroyed.
Think of the power GLorfindel had - able to drive teh Nazgul into the river more or less unaided by the power within him - and Galadriel was surely more powerful than he in her own right...