Firstly, and most importantly, I believe the Gods have flaws, their own ambitions and interests, and their own plans. They have their own reasons for doing what they do that exceeds what we mortals can now. They are also not omniscient, and don't know for certain what is going to happen in the future, though I feel that their educated guesses have a far better chance of being accurate than ours do. Again though, I reiterate that we should not confuse this improved accuracy (mostly due to their superior insight and wisdom due to being around for such a long time) with omniscience.
The fact that they aren't omniscient means that the Gods can and do make mistakes, and the fact that they aren't all powerful means that they can't just snap their fingers and fix things. If they make a mistake, they make a mistake and we suffer the consequences.
Following from this, most (but I don't think all) Gods feel benevolence towards their worshipers, and neutrality towards those who do not, in fact, worship them (mostly, anyway). Gods bestow their blessings as they see fit, and do not invoke their wrath among people for petty reasons. A God may curse a mortal for impious acts, and behave wrathfully towards a human for any number of things including general impiety, extreme hubris, oath-breaking, and murder. General behaviors which are displeasing to a God (but which aren't 'wrath' worthy) will not invoke wrath from the deity, but rather simply cause them to cease blessing the mortal and will cause them to revoke their protection from the mortal (and possibly his or her children as well). Deities also may set-up situations which are intended to test the mortal and make them stronger or groom them for a purpose that the God has in mind. These situations are not meant to punish, but rather make the person into a stronger human being for whatever purpose. Moving on from this, we have to ask ourselves, how do we figure out which is which? How do you figure out if your conduct is just poor or if you've actually elicited the wrath of a deity? Simply put, divination. While we may be tempted to simply sit and try to commune with the God in question, sometimes our own desires and what we want to hear can get in the way of what we should be hearing. We then stumble upon divination as the most objective way to get our answer, though if you have the capability to commune and divine, I would suggest a combination of the two.
All this in mind, I think the vast majority of Gods feel benevolent towards their worshipers and neutral about their non-worshipers(unless they wrong a devotee of theirs), does that make them good or evil? Well, no, no more than me feeling benevolent towards dogs makes me an intrinsically good or evil person. Good or evil becomes a matter of the person describing the God and not a matter of the God himself. A person seeing me as good or evil does not make me good or evil. Some people think I'm evil simply on account of being gay, for example, but that doesn't make it so. Thus, I find talking about the Immortals being 'good' or 'evil' to be useless, rather, lets talk about the benevolence, malevolence, or general nature of a God towards their worshipers.
|Amaterasu leaving the cave, source: Wikipedia|