You know what's great for employee retention without sugar-coating it? Pay your employee's correctly (you can't expect talent for peanuts), don't make them feel like they can't leave at a normal time, treat your employees with respect, offer a clear path of progress in the company (where you are now, where you could be) and one of the most important: innovate and excite.
The "respect" aspect isn't touched on much in these comments. It's shitty when your boss belittles your team in front of guests and makes you feel like you're all his "peons." No perks can fix that kind of disrespect.
I worked at a place like that once, they churned through so many system administrators especially and in the end found themselves in a situation where they were finding it hard to get system administrators and after all of that eventually fired the manager who had single-handedly damaged the company by that stage it was too late. So respect is something I definitely agree a company and its higher-ups should possess.