What is the best answer for the why should we hire you over the others waiting to be interviewed?

1- Sure, you have another respectable and skillful candidates , which I cannot speak about them, but speaking about myself , I am confident that I have both technical and managerial skills putting me in the place that I want to be on.
then talk about your great skills

It might depend on what you want to transmit: Confidence player assistant/employee: > Mainly you should hire me because I'm an assessed (tech, asistant,...) & not only qualified for this job due to my background & experiences, also because of the positive attitudes that I have towards the tasks, targets/milestones assigned to me.
I'm reliable and take care of my responsibilities so if you are chosing me, then your company will win a great asset with better return on investment.
Trusted experienced manager: > I know I have the skills as being an assessed & experience manager, I'm covering the requirements this position needs as previously developed similar role within international environment...
here might also be required from your end to explain me what you expect from me and why I should be involved in your project...
Please note that as I know I have Potential and Skills this position requires, I'm open to define a carrer plan and remuneration totally based in Milestones & Bonus so this way you don't incurre in any cost and my success will be properly compensated.
As having been several times in HR Manager position, I would recommend to avoid replying like "Why not?" or "well, you might tell me why I should work for you ,as I have other offers"...
if there is not proper feeling with interviewer...
this reply seems poor...
out of context...
and an excees of confidence is not always well received...
best,

well .. the other candidates may have the same skills that i have but what i m sure about it .. that they dont have the same passionate for this job .. plus when i work on something i put all my efforts and emotions to it .. so everyone can be related to my work and feel the love in it ..

Refer to your achievements - relevant to the position you are being interviewed for.
Add how by innovative ways and thinking you got to do a task more efficiently and/or save a project.
Take along (if writing) - copies of your work.
Show confidence when you speak.
Ultimately the proof will still be in the pudding.
Be confident, but not arrogant.
Display integrity and be sure to back up what you claimed in your written application.
On a lighter note, but don't say this: you've tried the rest - now go for the best.
:)

I believe the best answer is to draw on the similarities between the role and your experience and background, in addition to how your passion (to help, to grow, to learn, etc...) has led you to apply for this post.

Hire me and see for yourself!!

I not only bring in all required skills for the job, but give you also a wealth of experience in a variety of business and with a diversity of cultures.
That will be a great added value for the company.

Yes i know there are others out there but i feel i am good at what i do best.
Engineering is my food and give me a chance i can assure you that i will perform to the best of my ability.

It's all about skills the more lot's of skill in one person can get the chance to be hire.And that skills you can see in my cv.

Because,you were in this in more times in the beginning of your career the Challenge!!!!!!!

I have no information about others profile. But what I can tell you is about myself that I believe in myself, my abilities and skills. Secondly, there might be people more experienced than me but I am applying for a career, the others are applying for a job