Some Muslim scholars believed that a people's characteristics were determined by their environment, called their clime in some translations. In the days before the Crusades, they compared the Ifranj, the Arabic term for the Franks, to their climate. In their eyes, the Ifranj were a strong but barbarous people. That added up, because they lived in a harsh landscape that required them to be strong but not necessarily smart (unlike, by comparison, the Arabs). I think I read years ago on a post here that the Romans held similar ideas about the 'air' in Europe and Africa and in the Italian peninsula, so if I can dredge that up, I might be able to make a comparison because I suspect that that might be where these ideas come from.

Regardless of the origin of the ideas, they believed the Franks to be a rugged but uncivilized people by comparison to themselves. Many historians would probably agree with this conception, although 'civilized' is obviously a very loaded term that we should stay away from. At the very least the Medieval Muslim world was much more cosmopolitan and for a long time had a much more active intellectual culture than Western Europe did.

The Crusades brought about a really interesting period of interaction between Muslims and Christians, especially between 1099 (the conquest of Jerusalem by the Franks) and 1187 (the conquest of Jerusalem by Salah ad-Din/Saladin). Probably the most famous account of these interactions comes from the Syrian Muslim writer Usama ibn Munqidh. A lot of his works about the Franks are basically little comedic vignettes about differences in culture. They should be taken with a grain of salt, because he was writing for a Muslim audience, but we do think that he had a very good relationship with many of the Franks living in Outremer (one word for the Crusader kingdoms established in the Near East).

Two really funny anecdotes from Usama ibn Munqidh. The first has to do with the hammam, which was a bathhouse very common in the Near East but basically foreign to the Franks despite the Roman origin of the tradition. Another great example of Western Europe's claims to the legacy of Rome without actually making good on it. But basically the story goes that Usama is in a bathhouse that some Frankish knights are frequenting. One of the knights notices that Usama has his pubic hair shaved and is apparently amazed; he asks if he can be shaved too. The story continues, and the knight invites his wife into the bathhouse (big no-no) to be shaved herself!

This is one of the stories that I personally am more dubious of, but it illustrates a few interesting things for us here. First of all that Muslims like Usama ibn Munqidh didn't reject consorting with Franks out of hand, even though they were enemies. He even spends some parts of his writings cursing the Franks for their invasions, but is also apparently good friends with some of them. Good enough to be talking about his pubic hair with, at least. But more importantly to your question, it illustrates how some Muslims at the time of the Crusades saw their Frankish invaders: as uncouth, as not taking adequate care to protect the virtue of their women (think of the knight's wife), but as being generally good-natured and pleasant. Again, despite the fact that they're having regular wars with these folks, and despite the fact that Usama ibn Munqidh was a huge supporter of Salah ad-Din.

The second anecdote concerns a knight who was going to return to Europe with his family. This knight is allegedly one of Usama's good friends. He offers to take one of Usama's sons back with him and to train him in the knightly traditions of Europe (which at this point are still very much in formation). Usama absolutely does not want this, but he also doesn't want to offend his friend, so he basically begs off by saying that the boy's mother would miss him to much. In other words, Usama is good friends with a Frankish knight, good enough for the man to want to take one of Usama's sons as his foster child, but he has no desire for his son to become a European himself. I would bet that some of this concern has to do with possible apostasy to Christianity.

Another interesting account is that of Ibn Fadlan, who was an Iberian Muslim traveller that actually supplies us with one of the main accounts of the "Viking funeral". I know that's probably not what you're looking for when you say "medieval Europe," but it's a pretty funny account. He was basically in awe of the men that he met, saying:

"I have never seen more perfect physiques than theirs – they are like palm trees, are fair and reddish, and do not wear the tunic or the caftan."

References:

Hillenbrand, Carole. The Crusades: Islamic Perspectives. Chicago: Fitzroy Dearborn Publishers, 1999.

Ibn Faḍlān, Aḥmad, and Richard N. Frye. Ibn Fadlan’s Journey to Russia: A Tenth-Century Traveler from Baghad to the Volga River. Princeton: Markus Wiener Publishers, 2005.

McNeill, William Hardy, and Marilyn Robinson Waldman. The Islâmic World. Readings in World History,v. 6. New York: Oxford University Press, 1973.

Just a note, if you have any other thoughts about the thoughts of Muslims on certain things pertaining to the Christian world, Hillenbrand's Islamic Perspectives is an amazing source. One of my favourite history books.

God bless.