The reason why the evil companions are the only reasonably likable ones is because they're the only ones with somewhat believable motivations. The good ones don't really make any sense as characters because their motivations are just not believable.
Gale's background is like something written by an 8 year old boy that had some assistance in sexing up the concept by his 13-year-old brother. Like the 8 year old wrote the part about him having a bomb in his chest that would blow up the world if he didn't eat enough magic weapons and the 13 year old brother is how Gale is just so sexy because of his beard and his earring that he's banging the goddess of magic who has huge knockers.
The idea that good means putting others first in sacrifice of self is essentially postmodern-feminine and unheroic. Ancient portrayals of the tragic feminine hero would be like Cassandra (tells the truth in service of her people, is rebuked, goes mad), Dido (gives of herself freely to provide a future for her people under a strong king, Aeneas, but is spurned and cheated by the commands of the gods), Lucretia (kills herself to show that a Roman woman would rather die than be defiled; calls Romans to heroism to crush the evil Tarquins and so give everlasting freedom to all Romans), or Verginia (kills herself rather than submit to rape by the tyrannical judges; inspires the Romans to overthrow the tyrannical panel of judges). The ancient concept of the feminine hero is different from the masculine hero. The medieval Christian ideal of male and female heroism is not so far off from this.
The postmodern feminine heroic ideal is to sacrifice yourself for people you have never met so that they can go and be happy in some utilitarian way. Virtue doesn't really come into play because postmodern models of virtue are quite muddled. In BG3 (from what I have seen towards the end of Act I) the evil characters are the ones that are particularly devoted to some religious cult or to a martial people. The good characters are sentimental loner-narcissists obsessed with themselves and creating the appearance that they are good people.
As a side note, the notion that good characters also have to have an evil side is particularly confusing to children who are exposed to it in their japanimations or video games. Wyll's an example of this, in that he's supposed to be a good character, but he has made a pact with an obviously evil demon, obsessed with promoting his image as a perfect swashbuckling knight-errant. The evil characters are the only virtuous ones; it's just that they are dedicated to bad cultures.