[color=red]a. What was the best film each of you saw this year?
b. What was the best film every one of you saw this year?
c. What was the best film all of you saw this year?
\
In which case is
Many thanks.
If you meant to say you were addressing a group of cinema-goers who would watch films both collectively and individually, then I would firstly ask: What was the best film you all saw this year? Even that way: What was the best film we saw this year?
Then (on hearing the answer): What other films you may have seen individually you consider among the best?
“What is the best film you have seen (so far) this year?”
I really don’t see why there would be a point in trying to specify the individuals within the group if the people were to answer individually.
I’m afraid your question has some defect. Could you check, Eugene?
Would you give me a hint?..
Don’t take it amiss. It’s a small thing. You are already good at English. The hint is V-S order.
Then your version of the question would be:…
What other films which you may have seen individually do you consider among the best?
would work for your question, but I still feel it is unnecessary.
Of course, the question was unnatural in the situation, but what I was trying to do was make it sound more or less realistic.
Azz was trying to use ‘all’ and ‘each’ in the situation s\he imagined. ‘All of you have come here to enjoy The Scorpions, though each of you can expect different emotions from their performance.’—something like that was asked in my view.
As to my question, I still don’t see the neccessity of ‘which’ (you may agree here) and ‘do’ in the sentence (you obviously disagree). ‘What definition you consider the most suitable: stubborn or obstinate?’ Still insist on the ‘do’?
Yes, if it has to be a grammatically correct and acceptable question, Eugene. But in conversational contexts the spoken grammar (with stress) will accept it without ‘do’.
If it’s a question, then yes, “What definition do you consider…” is required. (Regardless of how informal it may be.)
Thank you for making me dig a wee deeper.
I found on the net: — Warren Ellis Q&A
Warren Ellis answered: “Of your works which you consider the best or which is
your favourite?”
–Which you consider best buy pound by pound? DHC or DHS?
I like both…but perfer … [DHC is the no. 1 direct skincare brand from Japan]
Perhaps those were not natives\not the best educated natives… Somehow it must’ve rubbed off on me, subconsciously, while reading. Young minds are so succeptible you know… 
When two choices are given, first ‘which’ is to be used, and then ‘better’, the comparative degree, not the superlative.
That’s incorrectly phrased.
That too.
Oooooh, yes. 
Overly rigid, inflexible rules.
Just standard for every other ‘educated’ soul.