I've ranked many sites in the top 3 without backlinks. The problem is I haven't been able to find out how yet. I was able to get a car related website to rank first in less than a week on google with only content. The keyword gets 10,000~ [Exact] searches per month. I tried to rank a similar site using the same method, which gets around 8,000~ [Exact] searches per month and it only has 2 pages indexed so far and it's been two weeks. The pages indexed aren't even the main pages.
Google can be weird some times.