Definitely agree on Helen Slater as the definitive Supergirl - the version in my Supergirl crossover series is basically an older version of her rather than any of the later ones, they just aren't as convincing (despite improvements in special effects etc.) She came across as having an innocence and a joy in things like flying and seeing Earth after a lifetime in an artificial environment that none of the others (apart from some of the animated ones) have done so well.
