It is subjective, but once you consider what Jak II offers more over Jak & Daxter, it is quite an improvement:
- Textures have been improved
- Animation has been improved
- More effects and more characters on screen
- Character models feature HUGE improvements
- Draw distance seems to be at least up to par with J&D if not better
- Freedom of doing pretty much anything at any given time
- Physics of breaking objects
All those things that I just listed require performance. All these improvements can be seen in the video I posted - for those who weren\'t able to download it, try this link:
Jak 2 Video.
Seeing how efficiant GT3 ran on PS2, I can only expect to see quite an improvement with GT4. Also, Ratchet & Clank used some form of the Jak & Daxter engine - having extensively played the game, I would say that R&C emphasizes on geometry while J&D was more balanced between geometry and textures. From what I can judge, Jak II seems to be an improvement in both ways, geometry and textures and all the other features I listed above.
Besides, I am not saying we should expect to see an improvement with every new game, but you should keep in mind that most currently available games don\'t quite hit the bar just yet and there\'s always a way to improve your code to make it more efficiant which in turn will make for better graphics [or other improvements].