I think there is a general consensus that elders quorum lessons are usually painfully bad. I have a few thoughts on why this is.
First, elders quorums are generally large--too large. With smaller groups you get more of a discussion dynamic. With a larger group, you get one of two results. Either there are fewer commenters and they are eccentric in some way, or there are too many comments that take the lesson off on tangents, or bogged down on one particular aspect of a lesson.
Second, elders quorums are too diverse. You have people in their 20s up to their 50s. People with kids, and people without. Married and not married. It's harder to teach to a diverse audience.
Third, elders quorums usually get the leftover room for their meetings, so they are frequently in the gym or on the stage. These are places of high traffic and echo, making it harder to pay attention to the lesson.
Fourth, elders quorum instructors are not always the best. Most of the talented teachers are teaching young men or other classes, or they happen to also be talented leaders, and so serve in a leadership position.
Despite these difficulties, I think that there are a few keys to a good lesson.
First is good participation. A good instructor gets participation with questions. but not just any questions--and this is the key--they ask good questions.
What makes a good question? First, the answer to the question can't be too obvious. This happens all the time. If the answer is "read your scriptures" or "pray regularly" then you have asked a bad question.
The question also should get at the heart of the lesson. It should be in the "trunk" of the tree, so to speak, instead of calling for speculation.
It's good if the question has an answer. Sometimes this is impossible because the best discussion questions will not have one answer. Still, I think that the instructor should have a model answer in mind, and should use that answer to move on to another topic.
In my mind a good lesson goes like this: (1) topical instruction (perhaps supported by authority) (2) good question (3) discussion of question (4) instructor's answer to question (perhaps supported by authority) (5) segue to next topic. Lather, rinse, repeat.
The other key element to a good lesson is story telling. The keys to making stories work with the lesson are: (1) the story has to be topical--like a really good illustration of something in the lesson, (2) its better if it actually has happened to the instructor, and (3) the story should be well told (not too long, not too short).
A lesson with a few good questions and one or two good stories will pretty much be a good lesson.
Every good lesson should also have a short testimony at the end.
I think if instructors spend their time thinking of a few good stories and a few good questions, and proceeded in this manner, EQ lessons would be a lot better.