Hi Julia... I believe it's all about passion -- because that is what motivates you to work on your website hour after hour until it's the success you always dreamed it would be.
I used SBI to create my first website and that was the single best advantage I ever gave myself in online business. It gave me direction all the way, but most of all, it helped me choose my website niche and actually think hard about it before I put in all that effort to making it a success.
First I chose lucid dreaming because its an amazing skill and I'm lucky enough to have nailed it myself over the years. I also knew it had huge appeal for other people. As an introvert I feel very passionate about my "inner worlds" and the topic of lucid dreaming just did it for me.
Then I chose natural vision improvement because, again, this is a relatively unknown area and after having success with it myself I felt compelled to spread the word. I know how frustrated people get by having to wear glasses and the fact that I had found a realistic solution gave me so much motivation.
Thirdly - just last week, in fact - I decided to make a website on Shetland Sheepdogs (Shelties) as I have two myself and they bring me so much happiness I can't even convey. After researching this niche with SBI I found it had suitably high demand and so began the website building process again. I love every minute because I am passionate about my topics and with the expertise of SBI behind me I know I cannot fail.
If I were to sum it up - choose a topic that you always end up talking to people about. Something you love to chat about, something that really gets you excited. Then go do the keyword research and that will ensure you're onto a profitable subject. Unless you live under a rock there is absolutely nothing stopping you from finding the perfect niche! Just spend a few days mulling it over, sleep on it, and your next winning idea will soon pop into your head.