Employees that are excited about their jobs often stay at least a little late because they are in the middle of something and don't want to put it down. Really good employees know how to manage their time so they can accomplish tasks within a set period of time. Staying late at one's job is absolutely not an indication that the employee is "excited" about their job. Maybe they were goofing off all day & suddenly realized that the task they'd been procrastinating about is due ASAP!
Another bad sign is when an employee is totally non-responsive during non-work hours. Baloney. My time is my time. Not the company's time. Non-work hours are NON-WORK hours. IF the company has given the employee notice of their expectation that they HAVE to be responsive 24/7, and is compensating that employee for such, then that's one thing. But if it's not part of the job description, then no company should expect it. In my line of work, employees that like their jobs are often on their computers at home sending and responding to e-mails as interesting ideas hit them. I love it when someone sends me an idea on Sunday evening because it usually means they're excited about something and can't wait for the "work week" to get moving on it. So your measure of a good employee is the amount of time that employee spends on their computer at home? Especially if they're working on something for the company? So the employee who values his family and spends little time, if any, on the computer when with his family, is a bad employee? Really?
On the flip side, I hate clock watching managers. They're the guys that walk the floor a little after 6:00 PM to see who is still there putting in the hours. I've yet to see one that shows up at 6:30 AM to see who is getting a jump on the day. Most places I've worked at have flexible hours and the people that show up early each day get shafted by the clock watchers. Fortunately, most of the managers I've worked for reward people based on what they do and not how many hours they take to do it. But you just said that a good employee who likes their job is one who spends extra hours working, and the bad employee is one who does not! People should be rewarded based upon what they do ... but what about that non-responsive employee that you criticized? What if that employee does a great job, well within their prescribed working hours?