I don't think James Marsden looks like Scott at all, he has a small frame and really doesn't give off Cyclops' vibes whatsoever.
Scott is 6'3, whoever is playing him should be at least 6'1, relatively young and of course really good looking.
Daniel Sharman is a bit too old for my liking, I'd prefer a young cast because they're gonna need to play these characters for 10+ years and Scott is not that old anyway, and that way you can adapt specific storylines that require them to be young adults, I'm not saying that they should start with the O5 when they're 15 like in the comics but starting with the main cast being 35+ would be a huge mistake.
I wouldn't mind someone like Patrick Schwarzenegger (the guy who played Golden Boy in Gen V)