With ragnell that isn't restricted (it shouldn't be normally since Ragnell reach 6-A only with the help of Yune) Ike would have a range advantages of tens of meters.
With Ether, Ike would have a AP of 4.17 and Aragorn a durability of 2.585, not a big enough difference to seal the deal but the sudden boost in strenght plus the sudden jump could take Aragorn by surprise. Also while only the second blow dura neg, the first can heal Ike.
Ike also might be more skilled than Aragorn, he beat the greatest swordmaster of the continent the black knight who also told him, that he became worthy of his father. Gawain/Greil was one of Dain's greatest general and no one could stand up to him.
From the Ike/Titania support:
"Titania: When I was a Crimean knight, I entered an officer exchange program and was sent to Gallia. Where your father was. On my first day, they held a joint training session in the royal hall. That's where I saw Commander Greil's might for the first time. He took on wave after wave of knights and defeated them like they were children. His swordsmanship was brilliant... The other knights barely had time to lift their weapons before Commander Greil had them on the ground. He was the mightiest warrior I had ever seen. My body... trembled at the thought of it."
From PoR chapter 19:
Volke: Your father was one of the preeminent swordsmen of his generation. That day, after he touched the medallion...Twenty soldiers had come for him. Twenty highly trained killers. Your father barely broke a sweat cutting them down. Then he began attacking his neighbors, those who had taken him in, concealed his identity, and called him friend. He slew them one by one, until your mother rushed in...thinking only to save her husband from himself.
Volke: Greil had lost his wife, and his grief was overpowering. To keep anything like that from happening again, he crippled himself. He slashed the tendons in his sword hand so that he could not wield a sword again. I took the job only because he had become someone my skill could handle. And even then, he was still far stronger than most men…
And even when crippled and whielding a axe instead of a sword, he was a match for Petrine, one of the Four Rider of Daein, Daein's strongest generals.
Ike is, even in the newer games like Engages, called the greatest hero despite the presence of people like Byleth who can defeat a whole squad of elite knight on his own with a regular sword as well as stomp Shez, whom even when unprepared managed to beat all 3 Houses alone at the mock battle.
