Good beds. I have been is several hotels lately that had fantastic beds. Big and comfy. One was the Hampton Inn in Germantown, Maryland, proving that you don't have to stay at the Four Seasons to get a good bed.
Good technology, including a decent sized flat screen TV. The cost of these TVs have come down dramatically, especially when you buy 500 at a time. I particularly like the Club Quarters, which caters to business travelers. They have good internet access, monitor connection capabilities, and iPod friendly devices. All good.
Decent fitness center. It does not need to look like the training room for the Vikings, but it should be clean, with at least a working elliptical, treadmill, bike, and a weight machine or free weights. If you travel often, this is really important.
Decent staff. Nothing takes a good property down like a bad staff. Conversely, nothing lifts a bad property quite so easily like a good staff, but that can only go so far. This is where more upscale franchises like a Four Seasons will distinguish why they cost so much. It's called a service business for a reason. A great examples is the Cosmopolitan Hotel in Toronto.
So the opposite of these, for me, generally defines a bad hotel. Dirty rooms, bad beds, old TV's with bad channel line-up and no or slow or costly Internet access, bad or no fitness center, and bad service. These are the hotels I try to avoid. I strongly recommend looking at online reviews before booking a hotel to avoid these. TripAdvisor is a favorite.
I didn't mention food, the restaurants, mini-bars, etc. That is important to some people, but I am not one of them, hence the omission.
Last, location, transportation accessibility, and cost are also key considerations.