It's also worth noting that all the major manufacturers deliberately design their products to be as compatible with each other as possible, to increase crew commonality; which has several benefits including increasing crewing efficiency (greater pool of pilots for given fleet), reducing training costs, etc.
The Airbus A320 family and A330/A340 family in particular are both designed to be as similar to the other aircraft in the family, handling-wise, as possible - I'm fairly sure that the flight control laws are modified for each type accordingly. This reduces the differences between flying an A318 and A321 for example to things like remembering not to rotate too much on the A321, and takeoff / landing at lower speeds on the A318.
As has already been mentioned, Boeing's recent efforts for the 787 are designed to facilitate training of pilots used to the 777 and 737NG flight decks, combined with, as far as I know, sympathetic / forgiving fly-by-wire flight controls. The 747-8 however is a hybrid of the 777 and 747-400 flight deck technologies.