People have different needs in a website builder, but I will attempt to answer define this the best I can. The easiest website builder I've come across is Weebly. That is if you're trying to create a stagnant website with a standard page structure and average graphics.

If you're trying to create a blog website, then Tumblr is the easiest website builder.

If you can pay for advertising using AdWords, newspaper, radio, television, etc. then a basic website might do the trick. If you can't pay for advertising, then you're going to have to blog and social network to compete online, against other websites, for visitors. If you are going to blog for visitors, then I would recommend WordPress.org as your website builder. WordPress is the easiest website builder if you're looking for competitive website options.

WordPress offers the the most SEO tools, social networking tools, the most attractive themes and compatibility currently available.