I'm sure that Aragorn is described as the best hunter and the best swordsman of his time and I'd have to agree that he was the mightiest warrior of his time.
Boromir was, I think, better than Faramir in terms of a battle. I'm sure that the recapture of Osgiliath by Gondor was creditied more to Boromir than Faramir, and there is little mention of his 111 day journey to Rivendell for the Council, but the few mentions of it describe it as being a very tough and very dangerous journey to make. I would give him the edge over Faramir.
The last few days, before seeing this thread, I have been thinking about who was the greatest warrior among men. I had made a shortlist of men from the different ages: Barahir, Beren, Hurin, Huor, Turin, Elendil, Isildur, Earnil, Aragorn, Boromir, with a few others like Tuor, Eorl, Faramir, as outsiders.
I personally think that Turin was the mightiest, with Hurin and possibly Aragorn the next in line.
From the original list of the thread, Gandalf and Gothmog were both Maia that were clothed in bodily form while Elrond and the WitchKing were both boosted by rings of power. So they should have an edge over the rest.
Of the rest, I would give Boromir the advantage, for the reasons stated above.
p.s. I have been reading these forums for a while and now I've finally registered and this is my first post. I'm so happy to be a Downer