I like Christopher Reeve quite a bit, but I have not seen this range you are so convinced of. Sorry. Sure, he went to Juilliard, he was a great Superman and I enjoyed him in small, supporting and humorous roles (like Noises Off). But most of his leading roles outside of Superman fell flat with a thud. Much like Gal Gadot's other roles (leading or supporting) that I've seen beyond Wonder Woman.
I am not going to hold his school or the fact he turned down good movies as proof of his talent. In the dozen or so movies I saw him in, he struck me as a really charming, charismatic guy with limited range. Gal Gadot strikes me as a really charming and charismatic woman with limited range. Is Reeve perhaps a little better? Probably. My main point stands: neither are great actors. Neither are of the talent and range we have seen from Hugh Jackman, Christian Bale, James McAvoy, Michael Fassbender, or Robert Downey Jr. This does not mean I don't prefer his Superman to all of their turns as superheroes, because Reeve was perfectly cast. And it does not mean Gal Gadot isn't a wonderfully graceful and transcendent Wonder Woman, just because she has even less range than Reeve.
Personally, this seems more like you trying to defend a childhood favorite from any criticism.