Newgroups wil never rival eMule's 700 million or so files, even with a news provider with a long retention, so I don't know who told you they have 'everything'.
I think people use it mainly for new scene releases, anything major and lots of minor ones are on usenet. Use
VCD Quality or
NFOrce to find out what's new and search for what you want using Binsearch.
It's also worth browsing newgroups in Binsearch to find ones that post stuff you like (genre music MP3s, DVDRs, games etc.) and keep checking back to them every so often for the new stuff.