I have no experience in LP'ing whatsoever, so this is purely based on intuition: I'd recommend finding a niche. The market for Let's Plays of big AAA releases (or bandwagons like Slender) is completely saturated and there is just no demand left. If you want to stand out there, you don't have to be just good, you have to be
exceptional (and even then it'll be hard to get noticed in the first place), and no one can give you any advice on how to be exceptional.
Smaller LP channels can be healthy when they find themselves a niche though. If they focus on a handful of obscure games that aren't covered by the big LP'ers, they can get a small, dedicated fan base of a few thousands, occasionally, which can be considered a success in such a saturated market.
For example, there's this guy on youtube, "iDubbzTV" who does Overgrowth as one of his main things. Overgrowth is an indie game in development, where you can play the development build if you pre-order. Because it's under development, and because it's very moddable, there's constantly new stuff, so it's easy to make video's about. Just try out random mods or showcase new features and you've got yourself 15 minutes of footage. Now, I don't really like the guy, I don't think he's insightful or amusing, but neither do I dislike him. And I haven't pre-ordered Overgrowth, but I am interested in the game, and might buy it when I get a better computer. So I occasionally watch his video's, simply because he has no real competition. That market (the OG community) is not being served, and he's doing quite well because of it: he regularly exceeds 10 000 views (and occasionally even multiples of that figure) on his OG video's. I honestly don't think he'd ever make that if he hadn't found a niche like that. I doubt he can make a living off it, but he'll probably make a nice extra buck.
You don't have to stick to your niche all the time, once you've reached an audience they'll probably be willing to check out your other stuff, as long as you don't completely break with what you were doing (going from Dwarf Fortress to Call of Duty doesn't strike me as a good idea, for example

).
So, if you're not into small, obscure titles, I think your chances of finding an audience larger than 100 people are really really low.