That’s a really good question.
I’d have to agree with Frodo and Sam - they did the most with the least of anybody in all the tales.
After them, we get into the more traditional heroes. I can’t decide on the order, but the ones I admire most are:
Beren, who undertook an impossible task (knowing it was impossible) and achieved it, even if it was achieved with help from friends, and I really liked the way he answered Thingol: “Death you may give me earned or unearned; but the names I will not take from you of baseborn, nor spy, nor thrall. By the ring of Felagund, given to Barahir my father on the battlefields of the North, my house has not earned such names from any Elf, be he king or no.”
Hurin, who fought valiantly - alone - against unnumbered enemies, only to live the remainder of his life in misery.
Finrod, for standing up to the sons of Feanor and going knowingly to his death to fulfil a vow of gratitude, even at the risk of his kingdom;
Fingolfin, for a whole lot, not the least of which is challenging Morgoth, one of the Valar, to combat, making all Morgoth’s servants afraid, and fighting so fiercely that even the victors didn’t ever want to talk about it again;
Fingon, for bringing peace between the sons of Finwe by his rescue of his friend and cousin Maedhros from Thangorodrim, even at the height of anger between the sons of Feanor and the sons of Indis.
Fingolfin, that’s a good list, and I think you could make a good argument for almost any of them. But I don’t really buy Elrond as a hero. He followed Gil Galad, hid in Rivendell behind the power of his ring, didn’t want to fight Isengard or Mordor, etc. Basically I see him as too complacent. He didn’t concern him with the events of his time except to give advice. He didn’t really even help Thorin & Co on Bilbo’s first quest, except to give them a good meal. Refused to allow Aragorn to marry Arwen until Aragorn claimed his throne. Basically he didn’t put himself at any risk, and didn’t really do much of note - caring only for his little slice of the past ages and nothing else. Even Galadriel, who was guilty of many of the same things, at least was more helpful to the fellowship than Elrond was.**
Side note (a bit of a hijack, but probably not enough for another thread) -
The bearers of the Three seemed very self-centered and isolationist. Cirdan just worried about his havens, never playing much of a role in anything since bringing aid during the destruction of Beleriand. Galadriel cared for Lothlorien and did nothing else. And I covered Elrond above. The only one with a ring who accomplished anything at all, beyond tending his own personal concerns, was Gandalf, with Cirdan’s ring. Is it possible that Sauron’s will was actually accomplished through the Three, same as with the Seven Dwarf rings – that even though he couldn’t directly control the bearers, they were drawn into a complacent, care-free state, minding their own realms and ignoring the events unfolding in the outside world?