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It's true that because the MC is the focus, he also carries the burden of making mistakes, sometimes for character development, sometimes for the plot. That can make people like the MC less, while ...
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Source: https://writers.stackexchange.com/a/47636 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#2: Initial revision
It's true that because the MC is the focus, he also carries the burden of making mistakes, sometimes for character development, sometimes for the plot. That can make people like the MC less, while Sidecharacters are free to be cool/flawless from the beginning and only show up when they can contribute something awesome. On the other hand, sidecharacters such as Zuko from Avatar the last Airbender are more popular then the Main character even though they make lots of mistakes so that they then can have character development. But thats all anecdotal. So what hard evidence do we have? Popularity polls. But a big problem with them is that they have a selection bias. If it's a poll on a fan forum the results can be quite different then an offical poll. And that isn't to say that the offical polls don't look drastically different then a poll would be that every reader has to take. You also have to factor in, that popularity poll voters apply "game theory" to their voting: If they know their Favourite (the MC) always wins, they might vote for their second favorite character instead to see him higher up. Let's look at Naruto: The titular Maincharacter won the offical polls 4 times, his Rival 2 times, and his mentor 3 times. So overall the MC is the favorite, but atleast 5 out of 9 times another character was more popular. And when polling a different subset of the readers (namely westerner instead of Japanese), the badass mentor always wins. On the other hand a similar Series "One Piece" always has the MC at first place (the trend that Westerners have the 2nd place as number one continues here). Here is what this Data tells me: Even if the MC is not the most popular overall, I would hardly call them the most boring part of the Story, even if critics like to present it that way. A lot of the casual fans still like the MC the most. And there are different types of readers with different preferences (that may also be culturally influenced). Some people often like the badguy or the rival more. Some like the dependable friend the most. Some like the mysterious badass.