After being on Newgrounds.com for a while and reading other people's comments I noticed that a lot of people think critique and personal preference is one and the same, but they greatly differ, here is a short definition of both:

'Critique is a method of disciplined, systematic analysis of a written or oral discourse. Critique is based upon an informed opinion, and never upon personal opinion. Informed opinion is accepted as being technical knowledge, personal or professional experience, or specified training.' source taken from wikipedia

'Personal preference is a choice ofpersonal taste. The selecting of someone or something over another or others.' source taken from dictionary.com

Here is a few examples that I found in the reviews, I will keep the writers anonymous:

'Too bad her skin is pale'- this is definitely a personal preference, the comment is directed at skin color(as to preferring other skin colors) rather than there being something technically wrong with the skin of the character.

'I love this painting. Tasteful and well detailed, and I get a bit of power from the painting; she's realistic and not exaggerated, and you get a clear sense of humanity rather than simple sexual objectification.
The biggest problem I have is some things seem a little off, for some reason her eyes and nose are at a disproportionate angle to her mouth. Her feet are a little strange too, the big toe on her right foot is twice the size of the other one and seems to take up a bit too much of her right foot, and equally on the left her toes are bunched together in an awkward way.'- this is an example of a good critique, first the reviewer compliments the artist, mentions the flaws with fact to support their comment.

'I don't like her long hair and the sky is annoying'- when the word 'like' is used then the comment immediately becomes personal. What is the reason for not liking the hair? Is it scribbled onto the head or you just don't like long hair? There should be a reason behind a comment like that.

'You should learn to draw pretty faces'- this again is a personal preference, what if the artist painted an old wrinkly woman? Just because she isn't 'pretty' doesn't mean she is drawn incorrectly.

When critiquing don't be mean and call someone's work 'terrible' or call the artist names.

Have a fact behind every comment (eg: the elbows are too high, they should be by the waistline), it would help to know the principles of art such as composition, balance, focal point, color theory, anatomy etc, to critique more sucessfully.

Try not to say that you don't like something, this immediately makes it personal, I'm not a fan of marvel characters but I appreciate the effort and the technical part behind it, so if I ever critique a marvel styled piece I will only point out the flaws and I will not say that I don't like their character's face, clothes etc.

Try and find something you like in a piece to not take away from the artist's confidence in themselves.
Don't give a piece a bad rating because you don't like it, if it's done correctly then give it what it deserves on a technical level instead.

I'm by no means a professional in art or critiquing, I'm just writing what I feel about this subject and I hope it helps others to be more considerate towards others and their works. Feel free to add anything else I have missed or might be wrong about, I'm happy to listen:)