Is that your sole criteria for a niche? Do you think you should go for a niche simply because it you spot an opportunity, or should you go for something that gets you jacked up?
My criteria is the latter.
My reason is simple: It's the fastest way to success. If I pick something that I'm passionate about, I'm going to enjoy the actual process, the means, and not just view it as an obstacle to my end, and through that way of viewing the work at hand, I actually value the work. I don't *sigh* each time I view everything I have to do - that accelerates my success.
Hence my daily progress is consistent, I don't view success as instant as many wish for. If the end is worthy, the means should be worthy, the end doesn't justify the means. I think the utalitarian attitude is extremely prevalant in the IM world, and causes many to be disconnected from reality, from what it actually takes to have lasting success.
So is your criteria for selecting a market to serve or a service to offer based on if there is an opportunity to make some money? This is the advice I see handed out to newcomers constantly.
Your best chance is to find the crossroads, where your strength / passion and market collide and you can channel that collision into providing value, that's when you'll make it.