What is good gameplay?

How do you define/describe what good gameplay is? What are the components? How should it be done right?

Is is the attempt to create meaningful illusions of something desirable, and the interaction in attempting to gain it?

I'd say that gameplay is the whole experience one gets from playing a game. This involves the game concept, the user interface/interaction, the visuals, the sound and the story -if present-.

gameplay can only be guaged by having many people play your game. The developer himself is probably the worst person to play test something for playability value, because he knows the quirks of the controls and won't view them objectionally.

a good gameplay is a gameplay that is simple to get the grip but hard to master, which is really catching you and lets you forget the time you spend on it because its worthfull time you spent on it.

Good gameplay is essentially anything that keeps you playing the game.

Components may be:
1. a primary goal eg. match-3, collect-em, shoot-em.
2. secondary goals, eg. extra task to finish a level.
3. player rewards eg. bonuses, power-ups.
4. smooth controls.
5. a game identity eg. character, setting.

Not sure what you mean by "done right" but it should be planned out thoroughly paying attention to every little detail if that's what you mean.

Good gameplay involves presenting the player with interesting choices, with reasonably foreseeable consequences.

I think good gameplay involves giving the player short term goals to keep them clicking. Plus throw in a dash of strategy to keep them going "ah ha! there it is". I have a link at work of this one site that actually did a study on what makes good game play. I'll see if I can find it tomorrow and post the link.

So basically whatever keeps the player addicted and playing and interested and not bored and feeling some sense of purpose or achievement?

Well I'd say it's 1000% easier to do if you're following a proven/popular type of gameplay (basically all top 10 games on BFG/Reflexive). Coming up with original gameplay like you described is very rare (Portal?)