i never liked any of the starfox characters final smash just because, in my opinion, they are way to easy to dodge, and the fact that all of them turn slowly make it very hard to react to someone who has jumped over you. About the only thing you can do is jet upward and try and make them get to high and ko them, but usually they just run right off.
I always thought that Marth had a fun final smash to play with, simply because it can shoot you across the entire stage, with the exception of some of the larger stages like new pork city, and temple.
Im also a fan of transformation final smashes, like sonic, wario, bowser, samus, ect. I would say that samus has the best transformation, turning into zero suit. She is probably the best character in terms of combo potential because if you know how to use her, you can get a very powerful three hit combo if the first move hits. Just use a fully charged B, and if that hits, follow it up with another stun from her down+A smash, then her forward+A smash, and you can deliver a good chunk of damage.