Something that's come up on BumbleKing recently is the question of whether people take the Sonic the Hedgehog franchise too seriously. I'll probably post my answer to the question in that forum thread once I get it figured out, but in the mean time I want to step back and focus on something broader: What exactly does it mean to take a work of fiction seriously?
After noodling over it for a while, I'm beginning to think that there are several different ways one can interpret the phrase. It can refer to how important the thing is or how big a part of one's life it is. It can also mean a desire for the work itself to be serious, as opposed to flippant. (This is more or less the meaning the BumbleKing thread focuses on.) I think there's also a sense that's a tad harder to define, but boils down to willing suspension of disbelief. It's that last sense that I'm going to focus on here.
In this sense, a work doesn't have to be serious for me to be able to take it
seriously. For instance, take the original The Legend of Zelda. It is a
game in which a boy in a
skirt fights to save a
kingdom from a giant blue pig. It's silly, if you think about it, but that
oddly-colored porker is taking over the world, and that pants-challenged kid
is going to save it!
That's the trick, I think: The conflict has to be real. You can have flippant, wisecracking heroes like Jack O'Neill, Sonic, and Tony Stark refuse to dignify their enemies by treating them seriously, but on some level, they should still take seriously whatever is going on between them and their antagonists.
I'm just brainstorming here, but I think the reason is that a good conflict is something relatable that helps us to stay grounded even in the midst of fantastic, comedic, or absurd goings-on. It creates a human element that makes it feel real, in spite of everything else.
This is a hard thing to quantify, and I really don't know if there's a specific place where I can draw a line that separates a conflict I can take seriously from one I can't. But I do think that a badly-implemented conflict can make it hard to take something seriously, as in Sonic Lost World (or Shadow the Hedgehog, lest you think it's just the silly tone). However, a really good conflict can make even something fairly silly, like the Portal games, easy to take seriously.