"Do you mind a little advice? Starfleet captains are like children. They want everything right now and they want it their way. But the secret is to give them only what they need, not what they want."
- Scotty in "Relics," written by Ronald D. Moore.
Star Trek: The Next Generation, October 12, 1992

Scotty may have spent his life being rushed through cleaning up messes that were other people's fault, but he did always did it with a passion.  There was never any doubt that, though the Enterprise could explode into a million pieces at any given moment, there was no other place he'd rather be, and the crew love him for it.

Meanwhile, James Doohan may have spent his career shouting gibberish in a bad Scottish accent, but can you name another man who single-handly inspired so many people to become engineers?  That's a solid life's work.