I like Gaspard because he's an ******* who is honest about being an *******. Celene is an ******* too, she's just more secretive about it. Briala is just stupid.
Gaspard is an a*ss because he wants to be, and can be. He's like a twelve year old troll in a chat room, being mean to people because he can, because he thinks he's inherently superior, more clever, more deserving. He wants the throne for himself, for his own glory, and wants to march on other countries in order to prove his country has the biggest. Lingering in the sweet memories of when Orlais was bigger, he can't help but have a colonialist mind, and for that, I can't ever like him.
He goes at war SOLELY for his own gain and glory. Nothing else. He goes at war simply because he thinks he's the sh*t that everybody needs, while he knows nothing about ruling a country to begin with and will just bring mess to it. So arrogant, pedant and full of himself, so little regard about who he kills in the process (because he did initiate the war, he's the one responsible for the majority of the loss, there). That, plus the fact he's not progressive at all, I just can't. Also, he has Chevalier's honor when that suits him too, even though I admit, when he decides to stick by it, he does.
Celene can be an as*hole, but it'll never be her first option, if she can allow it. She's quite the as*hole once pushed against a wall with no other way of escaping it, but it's used as self-defense, rather than a go-to option against everything she has to face. She wants peace, most and foremost, and wants to maintain her country in said peace, to spare any avoidable deaths she can. It obviously pains her greatly when she has to kill the rebellion at Halamshiral, especially knowing it'll cost her the person she loves most in the world, the thing that makes her feel she still is herself : Briala. She plays the Game because it's the only thing she has ever learned her whole life, and the only thing she knows how to use to make the world less sh*tty. She's less an as*hole than everyone makes her to be, she's just stuck in the Game, always has been, always will be. And she knows what the price of the position of Empress entails, and she accepts it, even though it makes her personal life really sh*tty. In that sense, I have respect for her, cause she can make decisions that are for the Empire's good, and not her own, she's capable of decisions like that, even thought the price is always too high. She's a well-written character, that evolved the way she is because circumstances made her be that way, but still managed to not become a complete and entire as*hole in the process. People will mostly mistake her will to keep on being Empress as a thirst for power, when really, it's more a "it's gotta be me, because all other options will f*ck this country up" thing (but the thirst for power is there, for sure, still less than Gaspard). She often does what she does for the Empire first, not as much for herself first. She knows putting Gaspard on throne will just ruin all the peace she managed to bring so far.
Briala, on the other hand, is nothing like stupid. She's an idealist driven character, she wants to change things for the better, and does it with little power she can. She does more to help than anyone else can claim to. I can never hate on idealists, much less calling them stupids, because I'd rather have them try change things, than others do nothing at all and keep the status quo forever. This world was built by idealists, every stuff that helped society be less sh*tty, was made by idealists. Not by people wishing to keep things the way they were. Briala does what she does for the better of her people, and she loses herself in that cause, never once wanting anything for herself, or her own gain. She's the one having the lighter shade of grey of them three, I believe, because she thrives where everything was against her to do so, and yet remains the most empathetic and kind character in the long run.
Anyway, I just wrote a wall of text about it, and stuff I feel right now might change when I'll read the rest of TME, but it might be unlikely the changes will be drastic. I doubt you'll answer any of it with anything other than a witty short sentence, so I'll just end this by saying : agree to disagree.