Contacting journal editor asking for final decision after all reviews were submitted weeks ago?
Make sure you wait at least 3-4 weeks if you do choose to write, so you're sure the Editor is not planning to ask another referee (this can happen if your paper has both positive and negative reviews). 

Be polite; asking for a "final decision" sounds too blunt, and is best avoided. 
Also, there is no need to remind the Editor that the reviews are done, they know that already. Something along the lines of "I would be grateful for any updates on the status of my submission" should be adequate.