Yesterday, Google's Matt Cutts posted a video saying that the number of pages does not directly impact your search rankings.
There may be a side affect to a site having more pages. Typically, sites with more pages have two benefits:
(1) They have more opportunity to rank for a more diverse set of keyword phrases, assuming your pages are targeting more keywords.
(2) Typically, larger sites have more links to their site and thus may have higher PageRank, which Google uses to set your crawl depth and for ranking.
But the number of pages on a specific site doesn't have a direct impact on your rankings.
Here is the video:
Image credit to BigStockPhoto for boy reading books