It's one of two. It's not inherently a flame war if done right. Let's take two examples.
1. You like the acting of Samuel Lee Jackson better than that of Keanu Reeves. I prefer Keanu's acting over Jackson's. We have a logical debate over it, explaining why we think the way we do, and having other people chime in in agreement. In the end we are decided to disagree or agree. It was just an exchange of opinions.
2. You and I argue and start screaming at each other that "Reeves is better!" "No Jacksons better you *****!"
So far I've seen mostly a more logical approach to this. There are the people who just say "Ygscst suks," but I also see a lot of good reasoning, logic, etc. as to why the Yogscast suck. This isn't a flame war, Mr. Manly, this is a debate. You will know when it becomes a flame war, because when it does, the moderators will shut it down.
i generally don't like a majority of the let's plays that are made nowadays. they were pretty funny once upon a time, before the whole "let's play" thing got popular, but now i just find people annoying. out of the few i've bothered to look at(from links in this thread, defending their little favourites), all i see is underaged douchebags, extremely annoying voices, extreme elitist, or people talking about their day while they play minecraft.
the yogscast is popular because of the things they did before minecraft.
I still like the Yogscast but not as much as I did during the beginning. Their SoI series got me hooked but they almost never update it and when they do the story seems to be moving so slowly now. I'm still following the series as they update though. I need to see how it ends lol. I also really liked a couple of Hannah's Let's Play series.
Most youtubers are terrible. They are in it for the subs and ad revenu, not for entertainment.
The only one I can tolerate this in is sethbling. Soothing voice, doesn't smack, slurp his spit, say "um" excessively (looking at you , ant twerp) and makes very informative videos.
Not to mention he's honest (said he makes his living just making vids).
The rest of them can pound sand up their asses for all I care. Just imho.