Jone Ashia'sXYZ is one of the 5 best fictions ever written by Indians.
vs.
Jone Ashia'sXYZ is one of the 5 best fictions ever written by an Indian.

XYZ is written by one Indian - Jone, but at the same time, the sentence is talking about the 5 best fictions written by Indians as well...
Is it necessary to qualify? Or both of them correct with no different meaning?

preferred usage (here in the US, at least) dictates the latter usage: ...written by an indian.
the idea is that the first wording doesn't make it clear that the books were authored by individuals, but the second does.

by the way, you can't pluralize 'fiction' (again, at least not here in the US - i don't know about commonwealth english): fiction is an uncountable mass noun, much like furniture, laundry, or silverware (think about the way you'd talk about more than one of those items, too, to make the point more clear).
you'd have to say 'works of fiction' or some other such construction.