Well, I'm an amateur, beginning comic artist who draw, in a style that is not comic-y, a long-form story, and I have no marketing skills.
So, I can't imagine being jealous of anyone's success.. unless they are also "an amateur, beginning comic artist who draw, in a style that is not comic-y, a long-form story, and have no marketing skills".
Otherwise, it would feel almost as weird as saying " I can't believe I can't make money with my comic when my friend make so much money with their auto-repair shop'.
But even so.. I'd probably be more happy for the other comic artist than jealous of them.
What I am jealous of, is the time people have. I'm always running after time. Right now I have some.. only because my back hurts too much to work, and I can't stay sitting for a long time either, so no comic drawing!
I'm depressed that I did not find a job that suits me AND allow at least one or two hours free a day on average, or allows days off. So yes, there is some kind of jealousy for people who have time, but I would say it's more envy than actual jealousy. I would like to have the same, but I'm not upset at them for having time, nor do I hope that they will have less time in the future (that would NOT make me feel better!)