It is definitely motivating for me. If you are an artist who takes their work seriously (more than just a hobby) then you need to be prepared to buckle down and throw countless hours into practicing. When I find an artist who can do something I can't, I push myself to learn why/how they do what they do, and more importantly how they likely learned it. Then, I'll work on it until I can do it to a level that suits my needs. It can take weeks if you're lucky, or years if it is way out of your depth, but the nature of art is that anyone can do anything if they maintain their passion for it.
As someone who models their style after the horror manga greats such as Junji Ito, Kazuo Umezu, and Hideshi Hino, I live in the land of envy, but it is that envy that also makes me get up and sit in front of my art desk every single day as I try to push myself to reach their level.