Oh, I had to think about this one!
My vote is going to go to Wally West, I think. Especially in his animated appearances, Wally embodies the heart and soul of the teams he’s on. He could be a little weaker or slower but never lets that define him. We even see in Justice League how losing Wally breaks the team. They just aren’t the same without him. They can’t be.
Wally doesn’t just hope they can win, he hopes they can be better. Better people.
On top of that, I think his speed would make him an excellent Blue Lantern.