I have played a few open mikes now. It's not a big thing in my life but serves to give experience in performance and it enables me to discover just what folks enjoy hearing the most. Each one seems to have its own flavor. There are significant exceptions to this, but I find that too many of the performers seem to follow a certain pattern, one that keeps repeating over and over between the mikes which I have attended.
They usually have good voices and play songs that are moderate in tempo. The songs may be either in the pop category (or acoustic rock if you don't think that is pop) or are written themselves. Although I don't normally care for pop, I recognize there is a reason it is called "pop". My own tastes are not mainstream. The songs written by the singers tend to be somewhat formulaic, introspective and angst ridden. Of course the creators don't think so. The Eskimos have 7 words for "snow" and what may seem boring to me is probably alive and vibrant, each one quite different to them. I wonder, "Would they would say the same thing about me?"
I notice that when the performers get to select several songs to play, they seem to pick songs that are very similar to each other. Rather than mixing it up, they pick what they like the best and stick to it. If you listen to enough music by a certain songwriter, you will find similarities that keep repeating, which is hardly surprising. The very best songwriters will have these similarities, a particular style, yet manage to keep each song different. Most do not. Most are not "best" of course.
What bugs me more is the focus upon the words to the detriment of the performance and, to a lesser degree, to the music. Here's what happens time and again. The performer gets up in front of the audience, a trifle nervous (which can be endearing, nothing wrong with that) with a guitar and a capo. Apparently no other instrument will work. All songs are capoed and fingered in C or G. They are strummed and once in a while inexpertly fingerpicked. There are no instrumental breaks, no lead-ins, no obligato, no bass runs, just singing to one's strumming. It seems they are either unable to play better or feel that the audience neither wants or needs to hear anything more than the words. I zone out on that stuff.
Now when you hear a professional (ie - someone who earns his living from singing) perform, it is a different experience. They know that more than angst-ridden lyrics are needed. They will combine a particular stage presence, some introduction (but not too much, please!), some humor or insight, a variety of keys, tempos and moods, along with some musical chops, and some instrumental breaks, and the songs will vary in subject matter and approach. Not every performer does all these, but the best ones will do many of them. They've graduated beyond open mikes. And, don't get me wrong, you will find people like the professionals at open mikes, only just not enough of them.