Criticizing method of another paper

I am writing a research paper, and am fairly new to writing. I am working on a research topic that has not been touched too much. There has only been one other paper published regarding the same topic.

In this other paper, they have a fairly strange methodological approach that almost doesn't make use of the method at hand. My paper is an 'improvement' of their approach, I am wondering what would be the best way to criticize their approach to present my own approach.

As Bob et al. failed to notice, we can actually do this..

Thanks for any advice.