They're not a suitable aquarium fish at all. I've known of at least two that have gone through the sides of aquariums. And at 4+ feet, they need massive tanks.
Best is pretty relative, but I think the pictus would be a great choice...comments here are making me want to go get another pair of them and have a trio but I'm already overstocked as it is:/
Some of the other syno's you can get your hands on would work just as well I think. But the pictus is probably the easiest to find/pay for and I think they make great pets.