GK1 was only on one CD, there's also a floppy version of it thats about 15MB or so. It would be perfect for this site, since its the best of the Sierra adventures imo.
GK3 was a mixed bag for me - the story just wasn't as interesting until the very end and the interface wasn't much fun. It feels like a diluted version of GK1 without the voodoo coolness. The vampire stuff was cool, but there was so little of it the game felt more like a geography field trip than an exciting adventure in the paranormal. The plot, puzzles, humour, atmosphere, music and voices were not as good as the original. For ?3.99 its probably worth it if you're a GK fan though, lots of people love this game but personally it was disappointing.
GK1>GK2>GK3
btw I have the graphic novel that came with the game in pdf format if anyone wants a look, it's a great scene-setter for the game (another thing that the sequels didn't have). Hmm.. on further inspection its seems GK3 did come with a graphic novel, dont remember one for GK2 but I wouldn't count on my memory.
