Copyright is a specialised legal protection, falling under the category of Intellectual Property, giving exclusive rights to a creator/author(s) of a creative work - wikipedia 
The rights were given and the duration of these rights differ from country to country, and as is standard with Copyright, is also limited by (country specific) exceptions, like Fair Use.
# International Standard
The Berne Convention for the Protection of Literary and Artistic Works (Berne Convention) (The Berne Convention of 1886) is currently the International Treaty which provides the scope for protection of Video Games as a Copyright. This protection can be drawn from the wide definition of "Literary and Artistic Work" Article 2 of the Convention, which reads as:
The expression "literary and artistic works" shall include every production in the literary, scientific and '''artistic''' domain, '''whatever may be the mode or form of its expression''', such as books, pamphlets and other writings; lectures, addresses, sermons and other works of the same nature; dramatic or dramatico-musical works; choreographic works and '''entertainments''' in dumb show; musical compositions with or without words; cinematographic works to which are assimilated works expressed by a process analogous to cinematography; works of drawing, painting, architecture, sculpture, engraving and lithography; photographic works to which are assimilated works expressed by a process analogous to photography; works of '''applied art'''; illustrations, maps, plans, sketches and three-dimensional works relative to geography, topography, architecture or science.BERNE CONVENTION, AS REVISED - Article 2
The issue with this standard is that it treats the whole game as a singular component while not defining what would be covered by such a protection and what wouldn't be. WIPO (World Intellectual Property Organization) itself recognises that complexity inherent in Copyrighting Video Games, saying, "Although Article 2 of the Berne Convention provides a solid basis for eligibility for protection of video games by copyright, they are in fact complex works of authorship, potentially composed of multiple copyrighted works." This statement, along with the fact that WIPO published a study focusing on a Comparative Analysis in National Approaches, shows that WIPO recognises that the application of Article 2 in not clear or absolute and different countries protect Video Games in drastically different ways. The WIPO (World Intellectual Property Organization) has stated in one of its reports that "there is no clear classification of video games and their protection will vary depending on each particular game and the elements that are part of it. In this sense, video games can be treated as computer programs and, thus, are classified as works of authorship; in that case, the source code for a video game is classified as a literary work. If pictorial or graphic authorship predominates, a video game may be classified as a visual arts work. Similarly, if motion picture or audiovisual authorship predominates, a video game may be classified as a motion picture/audiovisual work."[ The Legal Status of Video Games: Comparative Analysis in National Approaches]Copyright Registration for Computer Programs