First, Spain is only good because doctors get paid quite a bit per time they take the decision to transplant. I'm pretty sure this is coming everywhere, and makes the following comment far worse.
As for the first or last on the waiting list, that's a cool soundbyte, but that doesn't matter at all. It is still the case that most transplanteable organs are thrown away.
Now granted, that's not 100% true in all cases. If you're on dialysis and need a kidney, that might happen. But a true necessary organ, like a lung or a heart, beginning of the list, end of the list, doesn't matter. Even then, compatibility is an enormous restriction.
And of course, there's the counterargument everybody's silent about : if you're an organ donor, doctors will not make the same efforts to keep you alive. The decision to donate organs cannot be made postmortem, but must be done before the patient dies (at least 15 minutes or they won't even attempt transplant, ideally hours). Granted, if you're braindead for 2 months, not an issue.
If however you come in after a car accident with heavy internal bleeding, a doctor has a choice : you're, say, 80% likely to die, but in 30 minutes or so, not immediately. But if they extract your heart now, they can prolong the life of someone else by ~5 years with odds of some 50% or so (can be higher, can be lower).
At that point, a doctor will make the decision to throw away the 20% and ... well kill you.
But it gets worse : they won't use sedation (and though it's likely you're unconscious, it's not certain, certainly the level is uncertain (because there is more states between awake and coma than you'd think, some of those states involve paralysis, or you may be conscious but have severe nerve damage), as that would significantly reduce the odds of a successful transplant.
Now I'd hope they'd at least inject an overdose of morphine once the organ's out (because the patient at that point will, of course, die, no need for suffering).
Sadly, if accurately informed, I believe nobody would volunteer to be an organ donor.
And yes, the Spain thing is true in the worst possible case: doctors get paid, thousands of euros, for every time they declare a patient beyond rescue and go for organ harvesting instead. So not only is there a terrible incentive in the first place (the same as elsewhere, organs available for harvesting save lives of course), there's an even worse incentive in Spain's case.