Just a few things to think about before answering.

Pacing:  Do you think that a game feeling inappropriately slow or inappropriate fast is bad?  Do you like games that encourage you, the player to set the pace and be as sluggish or fast as much as possible good?  Do you like your games to give context to everything you do with no downtime? Do you feel that it's good for a game to slowly introduce you in a manner that feels organic or for you to experiment and fail at your own pace?

Mechanics: Do you like games with deep mechanics?  Do you prefer games with a variety of mechanics that are explored throughout?  Do you like these mechanics to be told to you via in-game tutorials or do you like to figure them out yourself?  Do you feel satsified when you master the game's mechanics and can run circles around previously challenging parts of a game?

Interactivity: Do you feel detached when there are cutscenes?  Do you think quick time events are lazy design choices?  Do you feel like you're a part of the world that's being displayed to you onscreen?  Do you feel that your actions and choices in the game are organic and streamlined?  Do you ever just lose yourself?

Challenge: Do you like your hand is being held?  Do you feel stimulated throughout the game?  Do you feel feeble or all-powerful at the right points?  Do you ever have to take a moment and think of new ways to approach obstacles or adversaries?  Do you feel that game is doing a good job of presenting its obstacles and new mechanics?

Polish: Do the controls of a game feel right?  Do you feel as though this is a game made for human beings, by human beings?  Does it feel right 'under the hood?' Do the parts make an overall grand whole?

Content: how interesting the game world is, not having boring overused level themes (fire, ice, wind, light and shit temples...), interesting enemies and cool looking villains. It can be about something that already exist (e.g. sport games) or create a whole word, like the Lord of The Rings.

Well I don't think there is one more than others because some are really good for focusing on just a few of those aspects and making them superb yet others can focus on other aspects and make them great as well.  Some games can be great with cutscenes and many games without them are great as well. 

A game with a nice story could get away with being less chanllenging while a puzzle game that is only a puzzle game could not.  RPGs can get away with a more open pacing to the game that other games can't get away with as well.  Also on pacing a game can let me take it more slowly and be ok but if it forces it on me it can be a killer.

Lack of polish can be a killer for some games.  If it controls too poorly and I can't do what I want to be doing easily I might just stop.

Something else to consider is the entertainment/ satisfaction value of the game.  This relates to replay value but it also can be just getting people to finish the game or keep playing games.  This could be things like the drop rate of rare items or extra content unlocked on the way.  It could be trophies or achievments.  It could just be getting to the next cut scene.  If the game keeps me satisfied I'll keep playing.  If I feel like I'm only playing a game for the sake of playing I tend to stop.

Content and story can affect the gameplay but those things aren't really gameplay.

And this is really a vague question with no answer because if a game screws up any of those points it heavily affects the others.

Completely agree, content is extremely important.

You mentioned mechanics? They're kind of a seperate thing to gameplay..

Ugh, this thread is aggravating.  Mechanics are gameplay, not the setting.

Content for me as well

Out of all the options POLISH seems to be the only requirement while the others seem like a matter of opinion or preference of gamers. Pacing, some players like being thrown into a world without a tutorial while some gamers prefer a step by step understanding of the mechanics. 

Mechanics, it can be simple or complex.. from simple leveling up to a multitude of complicated moves or calculations. It is a player preference. The simplest things can be complicated too when given enough thought and creativity. An example of this is Minecraft.

Interactivity, this element is closely tied to RPG, from conversing with NPCs to mindblowing cut scenes to engaging QTEs. QTEs can be very good in bringing in a certain level of interaction that is not present in cut scenes, for example in MW2 when trying to pull out a dagger from your chest, it tries to show you that you are involved that you are the one pulling the dagger not a computer. For me this is not gameplay but more of story telling.

Challenge, again this is a matter of choice thus why most games have difficulty options. Everyone plays differently and being able to provide the type of entertainment a gamer wants is the job of a developer.

Being polished is an essential trait for games as this is where you grab a gamer and tell them that this is a well thought out game that will bring you the entertainment you are looking for. You want to translate emotions in a story, or translate controller buttons into specific movement that feels very right for players. For example for a horror game, it wouldn't be right if you get a lot of ammo as it should be essentially a survival game and that creating fear through scarcity should be conversed with the player through the lack of ammo. Controls come in being polished as well, When players feel a huge learning curve with the controls then there is something wrong with it. A lot of things come from polishing a game and it separates AAA titles from shovel ware.

gameplay needs to be fun, and make me want to comeback for more. 

well if everything is polished well i really dont see how you could go wrong so yeah that.