Yeah, Corrin is the best emblem by a huge distance; the rest just aren't even in the same ballpark. The sheer utility in being able to change a large chunk of tiles to something of your choice, especially when placed on a Dragon unit, makes Corrin the solution to practically all problems Engage can throw at you.
And then on top of that, they gave Corrin Draconic hex to massively debuff enemies, and Dreadful aura, which stops the enemy targeted from moving for their next turn. And then ON TOP OF THAT, they give you the ability to debuff and freeze up to 10 (13 on Alear) units with Torrential roar, if they're packed close enough together.
The worst thing you can say about Corrin is the Engage weapons suck and the stat boosts don't tend to go well on Alear where you probably want her, but that's like complaining about losing $5, right after you won the lottery jackpot, it doesn't matter.
The next best are Byleth and Micaiah, because getting to dance and buff 4 units and a full map heal once per engage are just generally great. I don't dare order the rest.
Leif however is definitely the worst, and the only Emblem you might want to actively choose not to use for a bond ring.