Before the term 'First person Shooter' [or fps] became widely used many of these types of games were labeled doom clones [post doom that is]. I think the main reason id made doom was to create something more advanced than they had with wolfenstein.
Even though it was the same style of game, Dark Forces pushed the envelope firther allowing the player to do things they couldn't in Doom. So as much of a rip off as it may have seemed i wouldn't be inclined to label it as such.
Let's not forget all the things Star Wars [the film series] has ripped off over the years shall we
