The second original game is a masterpiece of CAMPAIGN DESIGN. Everything else is just fluff. The third game is an evolution of the second... the campaigns are three steps down. The fourth game – if they had added campaigns to it, with the depth of the second game, better graphics, and without the sudden shift to another world, the same people could have created the fifth game. The fifth game is optimal; the campaigns and storyline are at the level of the third game, and the system is halfway between the fourth and third games. I don't remember the first game. This is just my opinion.