Is AGILE the best system development method?

To specifically answer your question - "It's a NO". It's Not "THE" best method. It's "ONE-OF" those. 

Firstly, Agile is not a methodology. It's just a mindset, with proven success on selected projects. 

You cannot apply Agile to any / all projects. Waterfall model may still suit the best for your project, If the requirements are "clear". 

hope this helps..

Rgds,

ananth

Agile Methodology is about delivering what the customer REALLY needs. This is done through a massive communication between the project's stakeholders.

In software application development, agile software development (ASD) is a methodology for the creative process that anticipates the need for flexibility and applies a level of pragmatism into the delivery of the finished product. Agile software development focuses on keeping code simple, testing often, and delivering functional bits of the application as soon as they're ready. The goal of ASD is to build upon small client-approved parts as the project progresses, as opposed to delivering one large application at the end of the project.