Ramsey has a pre-contract agreement in place with Serie A champions Juventus as his deal at Emirates Stadium runs down.
Arsenal, who tied Ozil to a lucrative extension in 2018, were unable to convince a talented 28-year-old that he should stay put.
That disappoints former defender Keown, who admits he would rather have parted with a World Cup winner.
He told BT Sport: “Ramsey is at his peak but he’s leaving for another football club.
“It’s hard for the Arsenal faithful to take. I think he’s been harshly treated.
“I know there’s been the Ozil situation but if I was picking between him and Ramsey, it would have to be Ramsey.”
Keown added on Ramsey, who has been with Arsenal since 2008: “It’s a sad situation.
“He’s a victim of circumstances. He’s continued to mature as a player and develop.
“He’s a real leader in this Arsenal team. Playing in a deeper role, as he did under Arsene Wenger, I think that’s the best role for him if you want him and Ozil in the same team.
“He’s so important to everything they do. It’s the energy and the quality at the end of it. He really has become an outstanding technician.”
While questioning Arsenal’s inability to retain the services of a key man, John Hartson believes a fellow Welshman has been given an opportunity that was too good to turn down.
The ex-Gunner striker said: “I think the Arsenal fans have to get over it and I think it is an opportunity for the lad.
“He has got the chance to play in a great team with the best player over the last 10 years along with [Lionel] Messi in Cristiano Ronaldo.
“It is a different culture and a different league altogether and a big chance for him.
“Technically he is very good and he covers more ground than any other player.
“For me, his biggest asset is that he is a goalscoring midfielder and he should do well.”
Arsenal still have six Premier League fixtures to take in before bidding farewell to Ramsey, while a Europa League challenge appears set to reach the semi-final stage after securing a 2-0 victory over Napoli in the first leg of a heavyweight last-eight showdown.