Honestly, it sounds more like you're jealous of
  his compensation relative to yours

I know it's hard to sound convincing, but trust me, I'm not: I am well-compensated (and negotiated for such), perhaps even more than he (don't want to get too detailed here).

Where I am upset about compensation is that we've hired an engineer getting orders of magnitude less equity and performing orders of magnitude better work. Even if I can't change comp, I worry about how the "good guy" must feel & how to retain him if I just continue to "shrug off" the cofounder problem.