3D graphics can really aid a film with creating characters in fantasy based narrative that have weird and wonderful designs and the use of costume and make up design wouldn't do the character justice. This can be seen in the film Guardians of the Galaxy with the characters, Rocket - a talking raccoon, and Groot - a talking house plant that grew into muscle for Rocket to help him catching bounties.
The character Rocket would only have been possible with the use of CG graphics with the use of talking and getting across a personality of the character through the movements that Rocket makes, he acts and talks like a human rather than the animal, which would have been very difficult to create with make up effects. The character Groot could possibly been made with make up and costume effects, however the budget would most likely have been bigger than making the character entirely of CG and motion capture. The use of CG helps to create motion that most likely would not have been able recreate in make up and costume effects, however small parts such as growing extra branches, flowers and growing taller would have been difficult to create without CG. The CG works well when interacting with the actors in which some are designed with costume and make up effects that work well portraying the alien esk appearance compared to the main character who is of human descent.
In some cases, even though you can tell the amount of budget and time behind the CG does not work well. For example in the latest film in the Hobbit trilogy, Dain Ironfoot was introduced on a battle boar as he prepares for battle, in which both are in CG for ease in animation and aesthetics with the rest of the frame. However when Thorin stands with Dain, Dain is set entirely in CG, more so with the close up his face which I found quite strange when set next to Thorin who wasn't in CG. I felt that this did not work well as even though the graphics were stunning, next to a physical actor it looked strange.
I believe that for the authenticity of the character it needed to be make up effects to work and match with the other characters that were not in CG, to make it feel more realistic like the rest of the characters.
A good example of make up design is from the films, Harry Potter, another fantasy based narrative that involves magical creatures such as goblins. The goblin designs were made using make up and costume effects, that hold an incredible amount of detail and give a sense of authenticity and realism to the fantasy characters. Even through the goblins could have been made in CG, the sense of these characters being real heightens with the use of the make up effects and works well when interacting with other actors.