Me too. But then he had to slam into the eluvian like a child, and that's when he started looking pathetic to me.
I thought that was a good touch, and intentional. He starts off as this insanely powerful megalomaniac, with a fanatical Tevinter cult, Red Templars, a demon army, political assassins, and generals up the wazoo. He also has an insanly powerful elven orb, the Blight, a tainted dragon, and more. You also saw the hideously bad future where the very fabric of the world is torn asunder if he succeeds.
But the more you peel back his allies and plans, the more you discover that behind all that power and bravado, he's just an angry, petulant child lashing out at the world and the heavens because of his own disappointment. Solas even says as much if you ask him about Corypheus right before the final battle. (You've twarted all of his plans and now, like a petulant child, he'd rather smash the board than lose.)
I think Corypheus is a good villain, just a tad under-utilized. I would have liked to have seen one or two more scenes exploring WHY he is doing what he is doing rather than just focusing on stopping him, and possibly tying it into how the PC and companions might be going through (though that's hard since the PC comes from many different backgrounds and can have varying beliefs about anything). This would make him more complex and interesting.
As he is though? I think he's a solid villain for this game.