Answer:
Yes, he should be credited.
Step-by-step explanation:
Christopher Columbus may not be the first to discover America, but he was a major part of finding a new home for those who wanted to get away from the monarchy. If it weren't for Christopher we'd still be in the monarch world where we wouldn't have the freedoms we do now.
Besides, if you were to discover something on your own even though you may not be the first. You'd be credited as well for finding some things you might've came acrossed the original's did not. Sometimes there is more than meets the eye, that others may spot others cannot.