Hi guys! Glad to see heated discussions beyond the Grave!
Hmm, Aragorn versus Denethor, huh? I place my bets on Aragorn!
But honestly, the theme of Kingship is so very often repeated that it is surprising that no-one sued for democracy yet. Take a look at the original Hobbit. Bard the Archer is the rightful king of Dale. Did he "executed" the other guy? No, he loaded the old man with dragon loot, which the latter promptly embezzled! Denethor is hardly a joker like the old man of Laketown, but Bard seems somewhat in character with Aragorn (Are they related?)
On the serious note, Denethor had the military under his fist. After Pelennor Fields, Aragorn could be credited with being one of the Captains that saved the day, but it is going to be pretty hard to prove his kingship over Gondor. Note: to the point of his death, his followers are still blindly following his orders. It might take a struggle to root him out...