the problem is stuff like story isn't a mere superficial appendix to the games in question. Given that you defined the value in question as "fun" any objective look at a game being fun needs to include a whole lot of things. It seems to me though your argument about horsey's tries to tack on something stronger while using this moral intution

no point does it become impossible to objectivly judge things IN ESSENCE.

except it does because the values/relative values are very much in dispute. Again just look at the Arkham games which go for "cool looking ddr flow" over demands for technical proficiency. to evaluate this simply isn't an objectivity quesiton. it's not a question of grey zone limits it requires a conceptual shift becuase "agree with you" isn't something which only applies to clearly very superficial things like "horsey bad" (unless by horseys you mean "I feel the way the knight can move is gamey and messes up the natural flow of the game" which seems stupid but is a valid form critique).

If i build

the only way i can see this working is to make it my paradigm argument: from the granted internal logic things can be evaluated fairly objectively the problem is that whole logic can't be granted in the full evaluation of the game.

in essence

I just don't see how "horsey bad" counters the Arkham example. judging how good arkham was in essence was essentially a main point of arkham aslym reviews: they were evaluating a new type of fighting game basic mechanics on the (much more ambiguous term than you are granting) metric of fun. for objectivity to work you'd need to work from a preassumed base level of fun this mechanic should instill but you're also figuring that out.

you're getting your "AI program heads" argument by holding constant the design desires of shooters and building off of that but this assumption holds equally well for plot stuff and the flaws are equally apparent. there isn't this one fun metric there are a host of competing desires