I like Reis work, but he's of the Neal Adams school to my eye. Beautiful work for sure. but nothing that sets new boundaries.

Rivera is a solid artist, but I don't find anything spectacular in his work. 

Not familiar with Samnee's work Online search shows some nice stuff.

Young has a nice Watterson like style when he does the "baby covers"and its fun to see superheroes in that style. But they use him as variant cover gimmick too often. Still it's great to see someone with a more "cartooony" style.