It is very hard to convince people who have their mind made up. The passion for things that they do, beliefs that they possess or products that they like is very highly likely to trump any changes they see and be a part of. It is hard to convince people to move their business to yours when they are disinclined to change status quo.
The best group to target is the one that gets excited by alternatives.
Target those who want proprietary software; target those who love open source.
If the leading product promises to do everything, target the segment that wants only a few things (there is a market for that trust me) .
Target those who can afford high price or those who can't (but be wary of competition).
Target market by turning an exclusive item into a commodity or by making exclusive market out of a commodity.
Target women if market for men is saturated.
Target low salt content snack market; Target segment who don't care about it.
Target gourmet lovers ; ready-made food market
Target huge malls ; target small mom and pop stores
Target famous bloggers; target those who are vying for attention
Target youth; target older generation.
Target those who love tech; or those who don't.
Target men with hair; or bald men ;)
There are frankly so many choices, that there are no excuses left to not do something different. When you know your market, repeat and rinse the process till you reach market that is right for you.