I know for me, it's a matter of cross-promotion and making sure you use other media to link back to YouTube, if YouTube is your main channel you want to be using. My group has an account on GameTrailers, so any of my game reviews that get put on YouTube get thrown up on GT as well.
What's astonishing to me is that I end up fairing better in views on GameTrailers, but have better reactions on YouTube.
And yes, it's a little about luck and what your material is. Retro game reviews only tend to pull in oldschool gamers rather than a wide variety of people.