Waterfall is not better than Agile, and nor Agile is better than Waterfall. Each is suitable for specific types of projects. For example, Agile is perfect for software projects, while it's not applicable at all for construction and engineering projects (well, some are saying that it can be applied in such projects, but no one has proved it yet). Additionally, Agile doesn't scale well, so the larger the project is, the less efficient Agile as a project management methodology. Waterfall, on the other hand, is not a good choice of a methodology when it comes to software projects (because of the evolving and fluid requirements of software projects), while it's an excellent choice for non-software projects, especially construction and engineering projects. Waterfall is also used to manage mega projects, so it does scale very well.
So again, there is no better methodology, there's just the right methodology for the right project.