The following opinions are that of myself as myself and as the warden, not as the other wardens in which I or you have played:
Dog/Barkspawn is best companion. no one can dispute this while still being sane.
Oghren is a very reliable drunkard. Never change, Oghren.
In regards to the Zevran, I have always spared him. Everyone deserves a chance, of which he never had any: both in regards to his path in life...and against me in battle. (Cue arrogant pose, here). He's also a funny guy, so may as well have him around.
Sten is an honorable Qunari, and a good friend. His actions were foreign yet horrible, but I can understand that he did not wish to do what he did.
I trust Morrigan more than I trust Lelianna. I can trust that Morrigan will consistently be a scary shrew looking out for numero uno, but I do not trust Lelianna as a friend. Ally? Yes. Source of information? Yes. Friend? No.
I don't need a nanny, Wynne. Stop bothering me. I only keep you around because you do the heal-y stuff.
Fowlicide aside, Shale is a good person who's trying to rediscover themselves after who knows how long.
I always spare Loghain, sacrificing my friendship and comradery with Alistair:
Yes, he left the battle of Ostagar. I believe he felt it to be for the good of Ferelden. What if he stayed? It was the Blight (which he didn't believe it to be, admittedly), but would it be possible that the army could have stopped it then and there? If the army fell there Ferelden would be defenseless save for Alistair and the other warden (as currently played by myself)...and would Eamon's knights along with a few rag-tag bannorns and the treaties be enough then? You might not like his actions or his reasoning, but saving those troops at that point allowed for more soldiers to fight in the final battle.
Loghain's loathing (hue hue) of the Orlesians is understandable (although extreme in a way no one could understand without experiencing it themselves) by my warden, especially after hearing all about how they operate from Lelianna,though I personally would have allowed their Grey Wardens with open arms and barred the Chevaliers at the border. Looking into Loghain's history in the fight, I'd feel the same way about the country that allowed for the rape and murder of my mother, the theft of my childhood dog and companion, and the source of all sorts of wartime atrocities.
Loghain's worst mistake was relying on Rendon Howe as his political right-hand, which I do not consider a crime. Howe is the one who hires Zevran to kill the wardens. Look at Loghain's face when Howe brings the matter up: not only does he seem indifferent to plan, but he also seems a little worried, or perhaps disappointed (I've noticed him making that type of face multiple times in cutscenes. He never seems pleased with what he's doing). I wouldn't be surprised if Howe was also the main force behind the slavers and the poisoning of Arl Eamon, and Loghain simply accepted it (not saying that's good, mind). As a Human Noble (and as any other warden), it gives me great pleasure to single-handedly put Howe down.
When talked to, Loghain admits he made mistakes and wants redemption. He is a skilled fighter and despite his actions he is still seen by many as the Hero of River Dane. A symbol is a powerful thing to have, and the Grey Wardens accept all kinds of people...Something Alistair refuses to understand.
I haven't played through Awakening or Dragon Age Two, but I'm certain that Justice and Oghren (again) would be my bros, and I care for nothing of what I've read of the DA2 Companions...especially poor, poor Justice.
As for Inquisition...? It isn't out yet, but I'll probably get along with Iron Bull and Blackwall the Duncan look-alike at the very least.