Should a colleague receive authorship for identifying a research gap and reviewing a manuscript? A colleague of mine identified a research gap / problem and reviewed a manuscript of mine addressing said problem. Otherwise, he/she had no other contribution to the conceptualization and execution of the solution and to the writing of the paper. 

Does he/she deserve authorship? I don't believe so but I have acknowledged his/her contributions in the acknowledgements section. If this is not standard practice in science, I am more than happy to include his/her name in the list of authors.
Identifying a research gap and reviewing a manuscript does not seem to warrant authorship to me.

Things would be different if your colleague had also worked with you in designing the study, experiment or research project to address the gap she or he identified. Or if your colleague had written part of the manuscript, say the summary of the existing state of the art.

Different disciplines have wildly different conventions on what constitutes enough contribution to warrant authorship. For instance, the American Psychological Association offers resources and a helpful scorecard. At the first link, we find:


  An author is considered anyone involved with initial research design, data collection and analysis, manuscript drafting, and final approval. However, the following do not necessarily qualify for authorship: providing funding or resources, mentorship, or contributing research but not helping with the publication itself.


This does not seem to cover your colleague's contribution under the specific conventions in psychology.

I suggest you look over the websites of associations in your field, and/or of relevant journals/conferences, perhaps the venue where you are considering submitting your work. There may be similar resources specific to your field.