Google doesn't index every site at the same speed if website A adds a new page at the same time as website B this does not mean they will both be indexed at the same time. Why is this? In this article I will discuss why this happens and what you can do to be website A.
Let's start by discussing why Google indexes webpage's quicker than others. The reason Google will index a page from website A before website B is mostly due the frequency that you add new pages to your website. If you think about it if you are adding pages every day then Google is going to pick up on this and crawl your website more often in search of new unique content. If on the other hand you only add new pages once a month then Google won't index your new content as regularly.
If you want Google to increase the crawl rate of your website you need to add new pages with unique content on a regularly basis. However just adding any old rubbish won't help Google still needs to value the content you are adding. If you add a sitemap xml document to Google through your Google webmasters account this will help as Google can see when you add new content and from here you can also see the crawl rate of your website. Adding a sitemap xml can also give you a host of other statistics regarding your website.
Another way to get your webpage's index quicker is by getting links from other websites that Google indexes quick. For example if you add you content to websites like Digg which is a website that get indexed very frequently then Google will find your link and follow it to your website. Then from there Google can decide whether to index your webpage or not.
Making sure your new pages on your website are well linked from other indexed pages on your website will also help as when Google revisits these pages it will find the new link pointing to your new page. You should never add content on your website just for SEO purpose you should only add new pages if you feel your website visitors are going to benefit from this new content. If you haven't added an xml sitemap already I suggest this should be your first step.