Marth got buffed, and I'm not really sure why. He was already one of the best characters in Smash 4 with his tipper mechanic, and then they improved his specials in Ultimate?
Not sure how this will pan out, but I'm wondering if Marth will get any notable nerfs from the demo.
I mean, Dark Samus will basically play like Samus, so who knows? I think they're better than what most people think. Ridley, honestly could be really good too, but it depends on how balanced out his strengths and weaknesses turn out to be.
Unlike other large heavyweights, Ridley does pretty well in the air and gets a lot of range with his tail. I don't think he's top-tier material, but I think he'll be better than Bowser, Dedede, K. Rool, and Ganon.
At the very least, he'll probably be close to DK (mid-tier).