Judging a knife by the OOtB edge is like judging a car by how much gas is in the tank when you buy it. You would expect (or at least hope) that the knife is sharp OOTB (out of the box) but it won't be nearly as sharp as it can get. This is because it takes a lot of work to get a truly superior edge, and it can't be completely automated. So a human has to do a lot of hand/hand-machine work to do it, and that costs money. And there's a point of diminishing returns to consider; how much extra sharpness is the worth the extra money? How many will appreciate it?
Hardness with knife blades is generally expressed a number on the Rockwell scale. This number isn't linear; that is to say, 51 RC isn't 2% harder than 50 RC, it's a magnitude harder. At any rate, hardness has little to do with toughness. For example a glass or ceramic knife will be very, very hard- harder than most steels can get. But it won't be tough. You can easily chip the edge of a glass knife even though it's very hard. So you have to look at toughness, but edge stability is another factor. Many of the attributes we like to have in a knife are mutually exclusive. Raising one attribute often lowers another.
Hard knives may be a little harder to sharpen but not necessarily. Super Aogomi is often hardened to around 65 RC but it's relatively easy to sharpen. Steels with things that make it tougher, like vanadium, make the knife harder to sharpen but not physically harder. In a sense steel is little like concrete, or peanut brittle. The steel is like the concrete while the vanadium carbides are like the aggregate. Put another way the carbides are like the peanuts.
If you're asking which knives are the sharpest OOTB that's also tricky. Sharp can mean a lot of things. A polished edge may shave hair well and push cut so you'll call it very sharp...until you try to cut rope with it and it won't cut well. Likewise a knife that will rip through cardboard boxes all day seems sharp until you go to shave hair- then it's just ripping hairs out.
But as far as OOTB sharpness goes, Mora knives are usually very, very sharp. There's a little variation but you have maybe a 95% chance of getting a Mora that will be very very sharp. Bark River knives are pretty sharp OOTB, too. If you get one of the ones made in Taiwan (not China) the SOG Field Pup is sharp OOTB. And I'd say virtually every Spyderco I've ever seen was quite sharp OOTB.