Is an emphasis on "novelty" necessary in academic papers? I often come across papers which have a 'Novel' in their titles. In the content the authors go out of their way to explain how their work is the first to the best of their knowledge to come up with the results.

Isn't novelty a necessity in research papers? Is a separate emphasis really needed? What is the best way to convey novelty without sounding extravagant?
The authors need to make it clear that the paper makes a contribution and to be explicit about what that contribution is. Otherwise the work is not original and does not deserve to be published. (This excludes survey papers and such things.)

The emphasis on novelty need not, however, be placed so explicitly in the title.

Good ways of emphasizing the novelty are 


Include a short discussion at the end of the introduction stating explicitly what the contributions of the paper are.
Back this up with evidence in the body of the paper.
A proper comparison with related work. (As El Cid's answer states.)