Okey, now it makes more sense.
Let me guess if I got it right: You want to find the best keywords for your topic which also brings many pages in search results?
If your topic attracts 10 visitors from 100.000 possible results, your share would be 10/100.000*100=0.01%. So you need to get 50.000 visitors to get 50% market share. This amount of visitors is only possible if you own Microsoft web site, in other words, your site have to be popular and have good PR.
Now, your question "5-10% is okay and still good niche market to enter?" - that depends on many factors and it's hard to tell, you could tell me what's the 1st and 2nd number you're dividing in your calculations and what's your initial PR. But I don't think you should focus on numbers, you should focus on the idea and how you plan to survive in that market! You can enter any market with 0.00% visitors and with good business plan, you could have 100% in couple of years, it's all about hard working and achieving your goals.
Meanwhile,
good luck!
