You can use the canned Device Summary Report. Try running that and then tweaking it for what you like. It shows you data like the following. You can see most/least utilized by concurrent clients and usage.
The number under clients is ALL clients the AP had associated in the report's time span. The MAX clients are the clients that were on this AP at the same point in time.
One thing I do is remove Controllers from being pulled into this report and leave it at APs only. That won't skew the results.
Similarly, you can use a controller only report to see potentially over/under utilized controllers.