I've had lab mixes, boxers and great danes, and all were great dogs. The Danes had short lifespans though, and ate like a horse.
Also, I've known a number of folks with Recycled Racer greyhounds, and after they get settled down from being professional athletes, they were great dogs too. My vet raises sighthounds, mostly greyhounds and salukis, and swears by them.
".... I have always found that plans are useless, but planning is indispensable." - Dwight D Eisenhower