Look up Criken2 he doesn't do commentaries but just snippets of videos and edits them all together. He doesn't even talk too much either.

I don't know if these are genres but this is pretty much the styles of people I've seen on youtube:

1. Let's Players - Playing the game with some form of commentary and tries to add a little entertainment to it.
2. Achievers - 100% the game, play on ridiculous difficulties, or show how to get achievements and all that stuff. Speed Runs would also be in this.
3. Reviewers - People that just show off games, not necessarily multiple episodes of 1. Just to give people an idea of the game and tell them whether it's good or not.
4. Podcasters - Usually talking over gameplay footage about the game, life, or anything really. The highest form of these I would say are call of duty and battlefield 3 videos because they're round based and you don't need to hear all the stuff that's going on in the game. It's not like a scary game where you want to hear ambient noises or learn more of the story, it's just round based shooting matches so the commentary can talk about ANYTHING during this.
5. Walkthroughs - Basically a let's play, but the person doesn't do commentary and just shows how to beat the game.
6. Machinima - Videos based on the games, could be montages or drawn/flash art depicting game-characters and all that kind of stuff. Basically media about a game, while not really being gameplay or at least not a linear gameplay in the case of montages.

Which of these you are highly depends on what game you're playing. I think you're looking for the podcast, it sounds like what you want. It's basically a vlog, but instead of seeing your face the people are watching the game. But it depends, are you going to try and podcast with amnesia playing in the background? Because that's a game where they might want to hear how you're feeling about being scared and such and NOT want a vlog, because its not an action game or anything for them to be watching gameplay with no game-audio. But if you're into round-based games, mmos or doing some form of montage then it wouldn't matter.

Hope you can understand what I'm trying to say XD. I suck at explaining. I'll post some videos so you can see what I'm talking about.

Achiever - youtube.com/watch?v=zVdD8nw0d7I just gameplay, doing his best. Although you could talk over this if you wanted, but you'd have to do live commentary (which would make it an LP pretty much...) or you'd have to go back and record whatever you want to talk about and put it on top of the video, but who would want to do that when you're showing an ENTIRE game or bunch of achievements. It's just not how people do it due to them trying to focus entirely on how you're doing whatevers in the video. (That I've seen)

Reviewer - youtube.com/watch?v=W2eUbf2JQpY basically everything you say should be about the game cause you're trying to say whether it's good or bad and your thoughts on it before the video is over

Podcaster - youtube.com/watch?v=SRO2hj6Sta8 talks about what stuff he's using and then goes off talking about his favorite guns and all that stuff thus not really talking about what you're watching anymore

Walkthrough - should be self explanatory XD. LP with no form of commentary or anything, just showing the game being completed almost like a movie.

Machinima - youtube.com/watch?v=XaHRfqA6N9g shows funny moments kinda like a montage, throws music and stuff in there. During this if it had commentary you'd almost definitely want to be talking about what's going on though because the talking would otherwise be distracting (for this particular game).