Western Europe? Do you mean the landmass that extends all the way from the Atlantic ocean to the Pacific? You can walk all the way from the Bering strait to the Atlantic Ocean, and down to the tip of Africa.. thats a pretty large landmass and there was no gulf between Asia and Europe. (its pretty inhospitable in parts I agree, but the Mongol Empire reached the Mediterranean)

Also, perhaps, because the Arabs who were conquering were generally a land-based civilization, whereas the English, Dutch, French, Spanish, Portuguese, were all sea faring civilizations.

Certainly the Arabs had boats and knew how to use them, but I'm not sure sea voyages held the same cultural cachet in the ancient Arab world as it did in the ancient European coastal civilizations.