With the new PS3 and the Xbox 360 on the market, no one can expect the PS2 to have the best graphics around, but the older Harry Potter games used what resources they had much better than Harry Potter 6 does. While the past games had some minor bugs with cameras zooming into walls and people's heads suddenly turning inside out, that's nothing compared to the latest mess. Even by PS2 standards the graphics for Harry Potter and the Half-Blood Prince, quite simply, are horrendous.
The characters are like choppy, colored boxes. Their faces move in odd positions while they're talking that make them appear to be chewing large wads of gum, and the voice acting is so low and poorly done for most characters that they're impossible to understand without subtitles. Even the cut scenes don't bother to step up the graphics any.
What's worse than the graphics is how sluggish they make the controls. A more in-depth look at the controls for Harry Potter is discussed on the next page, but the graphics seem to mess those controls up as well. Objects are hard to see, and often the boundaries around an object seem to stick out much farther than they should, causing you to bounce off objects while flying that you never even saw.
The only improvement to the graphics is the castle, which looks a bit more detailed than earlier games and doesn't create as many glitches while running around or trying to climb stairs. But this comes at the sacrifice of a smaller world and fewer rooms to explore.