It comes down to an enjoyable connection. I can tell the difference almost immediately. And thinking about it typing this. Some make me smile because we were so close. Others have not created that spark.

I may sound like a hopeless romantic here, but if she's not into doing a decent amount of foreplay, then I'm not into her (literally). Hardly ever looking into my eyes while love making is a turnoff, and so is not moving her hips "to the beat". Lastly....not smelling pleasant, overall speaking, is rather foul. Hope that answers your query, and I also hope that wasn't too vulgar or explicit in detail.

A woman who just lays there is no fun. I want her to feel as good as I do. If I wanted someone who just laid there, I would buy a blow up doll. On the other hand, a woman who bounces around like she is having a seizure is no fun either. It makes me feel like she is making fun of me. Her looks don't enter into it. I've already decided that she is cute enough or sex wouldn't even be on the menu, and besides, beauty is only a light switch away.

I think any sex that results in climax for both parties, however it happens, is pretty good sex. With that said, if one or the other is preoccupied and not mentally into it, that will probably put the kibosh on achieving aforementioned climax. This scenario assumes the sex is between a couple and not just random sex with someone you met at a club. In that situation, there are other factors that contribute to the potential excitement and/or lack thereof. One could spend a lot of time writing an analysis on this. LOL!

I think we are all different
For me, it is the feeling she is into it
Nothing worse than someone laying there like I am bothering them, please just cum and get off me

The failures I've experienced were due to my not being there mentally. There was no pursuit and catch (I mean in a romantic sense) or their desires were not my desires (a gal who was... into more kink than I, kink including pain and submission ideation... wasn't my thing at all).

To each the requirement to communicate their desires and to attend to their partners. Is, I think, the best way I can put it.

I wonder why we are not getting much response from the female members? I think that would be some interesting things to read.

I think incompatibility would make it less good. Maybe the actions that turn you on are not actions she's comfortable with, or even familiar. Also, if she is not connecting, not really feeling like the it's the best thing to happen since sliced bread, then it can be a drag. I personally would not want to be with someone who was just going through the motions to please her partner. I would want her to be as into it as I am, and hopefully she would be enjoying it even more.

I would agree with stinkeye_a, if you can't give as good as you get, it's not really working. I like for my partner to climax more than I do.

I wouldn't classify anyone I've had sex with as not good. Some were definitely better, but in the case of the lower ranking experiences I would put the blame on both participants. You really do get as well as you give most of the time. I've had a couple of partners with whom I was never in synch. Was it her? Me? I can't say, but WE weren't the best combination.

I have had partners who were unresponsive to almost everything. Maybe, I didn't learn what they would respond to. Maybe she wasn't sure how to respond to somethings. That was the case once. Afterwards she said that she tried not to make noise because her ex didn't like that. WTF?
One partner was very obviously not into the occasion. She said she tried to force herself to want it because she liked me, and was uncomfortable with being attracted to women. That one messed with my head for a while.

In general, I think most unsatisfactory experiences I've had have been on my end fortunately none of those came (not a pun) the first time with any woman, so at least she knew that I could do better.

Personality and willingness to explore are the most important things to me. A boring girl is about as bad as a girl who doesn't smell good. I'll make a polite excuse and leave for either of those reasons.

Very quiet, lack of feedback, and / or lack of obvious interest makes me lose interest. I ask for what I want. I ask for feedback feedback on what I'm doing and what she would like me to do... I agree with @Buddha, there needs to be an interactive and interested connection.

Thanks for posting this. It was refreshing and very validating to see the commonality in our responses.

Several factors make sex "bad". Hygiene is a big factor. Being stiff and unresponsive are two more. Being OVERLY responsive is another. Low self esteem on the womans part such as stating that she is too this or that and won't have illumination of any sort.

For me it all comes down to her being confident. Size, shape, color of skin or hair, lack of hair doesnt matter. If she can grab me by my hands or ears and either verbalize or direct me towards finding bliss for her and eventually for me then its a good session.

This was a great question.

I'm no prude, but I don't like profanity in the bedroom. I mean seriously who wants to hear that kind of language from a child.

That's a variation of a Jimmy Carr joke.

A dead fish, smelly body, bad breath

This sounds really bad, but I have a quota. A minimum number of orgasms she needs to have. And I fully understand, not all women can have multiple. But, standards are set for me. I enjoy the act, the connectivity, the embrace, the intensity, the various positioning, fingernails rpiping skin off my shoulders, etc... My own finish is ancillary. If you're going to do something, do it well. And too much of a great experience is never enough.

If my partner was not open minded or would not reciprocate (oral for example)

I think lack of effort and not caring if they please you and not communicating her discomfort or unwillingness to do something. This can mostly be prevented by getting to know the woman before you hop into bed with her. If each person is truly there to make the other person happy that is the best. I can't imagine having lousy sex with the woman you love or feeling the need to tell someone about it. Otherwise a lay is just a lay and you get what you get and rating 1-10 is not going to matter either way.