Middleware costs money too, and it may not suit your vision anyway so you have to redesign parts at your own expense. The reason people use it is to have a faster turnaround for games and start realizing the vision of the game sooner.
As far as assets go, all major publishing houses have a shared pool of assets they can put into games. I don't think it is a significant issue. Sony makes available a large amount of art assets and information to developers so they can develop better games.
As for the Haze example, they cheated. They only used one model anyway for the enemy soldiers. The Wii developers if trying to make the same type of game to the best of their budgets will probably spend as much as the HD developers on their 2nd/3rd generation titles. Engines/tools/libraries of art assets all have to be made, they are cheaper yes... but they have to be made.
Tease.
