The reputation of a researcher: number of Citations vs Quality of publication From my social circle and from google scholar I learn that sometimes a trendy work with very less scientific depth gets more citations compare to  a less trendy work with high scientific depth. So the question is how to determine the quality and reputation of a researcher?
Quality is not easy to define in general and this is even harder when it comes to scientific work or even scientists. One may say that any judgment of quality is subjective and hence, as Pete L. Clark suggested, you have to form an opinion yourself, e.g. by reading the articles/books or listening to talks if you have the chance. You may also ask colleagues about their opinion to help you to form your own opinion. To see that quality is subjective: The formulation of your question suggests that for you, high quality work has to have some "scientific depths". For other people "high quality" may mean "great and simple ideas" (which may not be too deep, after all).

Reputation, on the other hand, is something that is more related to a community, so you can get a good impression of someones reputation if you ask colleagues who are in business for some time. To see that quality and reputation are not the same thing you may get a response like "He/she has a good reputation in the field but I do not like his/her work very much."