Earlier quoted context omitted.
> Does that mean I don't deserve to have the bargaining power for the best deal for myself? No, I do not believe you are entitled to a wealth transfer from people who are better at your job than you are. (Or, to put it another way, you're certainly free to do a little collective bargaining if you'd like, but the World's Greatest Widget Engineer has no reason to join your union.)
Why hasn't he been promoted to management? Most companies don't have a career track for the single most productive IC ever, and he's probably capable of improving other people's work anyway if he managed them.
Even if you did promote your best engineer, that just means that a different employee at your company is now your best engineer and the same dynamics apply. (Until, of course, you promote everyone competent to management, and then your organization is doomed to slowly suffocate itself. Then it's beyond saving, union or no union.)