The Introduction

A well-written introduction:

Sets out the argument

Summarizes recent research related to the topic
Highlights gaps in current understanding or conflicts in current knowledge
Establishes the originality of the research aims by demonstrating the need for investigations in the topic area
Gives a clear idea of the target readership, why the research was carried out and the novelty and topicality of the manuscript
Originality and Topicality

Originality and topicality can only be established in the light of recent authoritative research. For example, it's impossible to argue that there is a conflict in current understanding by referencing articles that are 10 years old.

Authors may make the case that a topic hasn't been investigated in several years and that new research is required. This point is only valid if researchers can point to recent developments in data gathering techniques or to research in indirectly related fields that suggest the topic needs revisiting. Clearly, authors can only do this by referencing recent literature. Obviously, where older research is seminal or where aspects of the methodology rely upon it, then it is perfectly appropriate for authors to cite some older papers.

Editors say, "Is the report providing new information; is it novel or just confirmatory of well-known outcomes?"

Aims

It's common for the introduction to end by stating the research aims. By this point you should already have a good impression of them - if the explicit aims come as a surprise, then the introduction needs improvement.