Do any of you submit links to your own directories, from high traffic sites? I have seen many directories with some very popular sites listed in them and i'm sure that the owners of those sites didn't submit to directories. Or i might be wrong.
I think that if you want to be your directory to be successful, You have to have best sites of your niche listed in your directory, otherwise nobody will trust your site. As those big site owners are not going to submit it, You need to add it yourself.
Your best bet would be to advertise - both as large adverts and small directory listings on directories related to your niche. You'd be surprised who actually submits to directories and who doesn't. I personally received an e-mail and link submission on one of mine from by far the biggest company in my niche.
Good advice andriusk and repped. Make your directory what YOU want it to be, not what the spammers hope it will be.