The fastest processor you can get in a ThinkPad at the moment is 2.0 GHz. The highest video is ATI X1400. These both produce less heat. Also, the Macbook is very thin, a stylistic decision, not an engineering one. My guess is the engineers had to figure out a way to make it work, and keep the general dimensions the same as the G4, so they had there hands tied so to speak. The ThinkPad, or whatever they are calling it these days, is somewhat thicker.
Try and see if there is a way to under clock your CPU to 1.8 or 2.0 GHz (the IBM options), and under clock your video. That might produce heat ranges around the same as what you’re seeing from IBM. My guess is if you find a way, you probably won’t do it 🙂
If that’s true, then the tradeoff Apple made to give you a more powerful machine (heat), you find acceptable too.
Cheers!