So I read through all of this and only have the following to say:
The mistake of landing on a taxiway is pretty close to unforgivable IMHO. As a private pilot I prepare for any airport that I fly into: I study runway configuration, what to expect, frequencies, etc. John Wayne (KSNA) is a simple airport with only 2 parallel runways. If you are cleared to land for 20L you verify that you are on the left of the big 20R. The weather was clear, and it is very easy to see. Fold has likely been there before because its close to where he lives.
If there is a (big) airplane below in front of you in the flight path, you go around instead of land: someone must have made a mistake.
Han Solo should not fly solo anymore.
Here's why. I agree with most posters completely that you CAN mistake a taxiway for a runway and it CAN happen that you mistakenly land on one (in the daytime. Night it's not really possible to mistake one for the other, when they're properly lit)
However, when you say on the radio 'hey, was that 737 suppose to be on the runway i landed on?' then we have a problem. You DO NOT EVER land on a 'runway' that has an aircraft behind you when landing. (in front of you is a slightly different story). You don't fly over the top of a 737 and land past it. The first rule of landing is that if anything is wrong or out of place, go around and try again.
If there is an aircraft in front of you on the runway and you can see it is accelerating, you CAN land behind it provided it's safe in your judgement. Flying over the top of a plane and landing, just no. Don't ever do that.
ETA: There is no airport in the US that I'm aware of where you fly over the top of stopped aircraft to execute a landing. Certainly you can fly next to them as they're holding short of the runway, but you don't fly over the top of them. In this case, I agree that the 737 was likely holding short of 20L waiting for Ford to land. It would then cross to the large runway and takeoff. But the rule still applies. If there's a plane parked on what you think is a runway, you DONT FRIGGIN LAND.