Problem is that meaning or deep emotion is usually unilaterally cruddy ones. I'd much rather spend the majority of my life drinking milk and ginger (chocolate milk and something not ginger, anyway, since ginger tastes ruddy terrible to me) than spend most of it gargling feces-draino cocktails. I got tired of the "world is mud" bullshit back when I actually was stuck in classical literature for several years straight (never again).
I'd strongly say there's a lot more room to be explored in regards to upbeat and healthy interactions between characters than most everyone gives credit, though. You don't have to have shitty people being shitty to one another in a shitty situation to impart meaning, and positive emotions can get just as gorram deep as negative ones. Slice of life can be fluffy without being vapid. High literature may tend to disagree with that, but there's a ruddy reason I don't read that well constructed drek anymore.
Terry Pratchett's books are a good example of optimistic books with a deep meaning.
Pratchett's books also absolutely
love their complex characters and non-linear morality. That's a big part of why they're interesting, the people are genuine and believable despite the often absurd circumstances in which they are placed and the farcical send-ups of archetypical plots in which they take part.
On a somewhat related note, "good" cannot exist in a vacuum. It's a meaningless idea on its own in the same way that "cold" is meaningless without heat.
Cold can -only- exist without heat. Cold is -defined- as the lack of heat. If there were no heat there would be -only- cold.
EDIT:
There's a word for concepts like that that are abstract things defined simply by the absence of a concrete thing (cold is the absence of heat, dryness is the absence of water, silence is the absence of sound, etc) but treated lingustically as if they were real in themselves; but I can't remember what the word is. Do any of you know?
Sorry, I meant that in terms of linguistic concepts, rather than physical laws -- we understand the meaning of "cold" because the meaning of "heat" or "warmth" exists; they aren't binary opposites in the sense of good and evil, but conceptually each relies on the other; even if we were to express things in terms of degrees of heat/sound/whatever, there's the implication of a point at which there is
no heat/sound/whatever, thus we define temperature, loudness, &c. not just based on an arbitrary scale, but also relative to that point of absence. I probably could have expressed myself better if I'd just said that meaning arises from conceptual heterogeneity -- there must be an alternative to or variations on a thing in order for that thing to have meaning.
Oh, it's on the tip of my tongue. Damn, that's going to bug me for ages. :|