Hello ajaykusumseo,
I think video marketing is a good way to promote your business, for many reasons: video is a new trends, and people like to see videos, it's original and different... So many reasons !
To choose the best video agency for your project you have to think about: your target, your goal, your needs, your budget...
To have different ideas about the work of video agencies you can take a look on these different companies. For example:
1) Demoduck is specialized in explainers and educational videos. If you want to explain something I think it's a good idea to take a look on their website. They have a video which talk about the Netflix concept and how to use it !
2) Cartoon propose different types of videos like TV commercial, product animation, and explainer video. It can be interesting to go on their website and watch their portfolio. The 2D animation is very impressive, and if you want to do a video like this kind, you will enjoy their creativity and their quality. If you prefer 3D animation, they also have some various examples on their website
3) Skeleton propose very different kind of videos. Their portfolio is huge, and you can see 3D animation or promotional video. They have a different way of thinking, and propose original ones. To watch their work
But you can find a lot of agencies on internet of course, and make your own idea of video marketing sector
I hope my comment will help you