Hi Chris,
You're quite correct in so much as most people are chasing niche markets these days. However, finding that magic combination of little competition, high sales volume and good profit margin is harder to find than a bag of Hungarian Chicken's teeth.
Little competition (very possible) good profit margin (possible) high sales turn over (next to no chance)
As soon as a product has a high turn over, it attracts big competition because of that sales volume. That level of competition then brings the price down, so the good profit margin then disappears as well and your niche market then disappears overnight.
The best you can aim for in reality is two out of the three and be happy if you can find that because having a slower sales turn over will usually protect that market from major competition and have it remain more niche.
The big trick to using a niche market model is to not just find one niche, but many. That way you increase your margins by variety, while your niches are still protected due to the slow sales volume.
In other words, your not putting all of you Hungarian Chicken's eggs in the one basket!