While I might not go THAT far, I agree. Portal: Prelude was a great mod. The Portal chambers were good and the story was good, but it was made as an extra in the Orange Box it seemed to me so it was short and all the levels were designed so that the average gamer could play them. Fun, but a bit too easy for me since I like games with a slight challenge and difficult puzzle games. Portal: Prelude, on the other hand, throws that completely out the door, says “Screw the average gamer”, and raises the intensity level to mind-numbingly frustrating.
I think my only problem with it was that it was too much trial-and-error. There were chambers that were completely speed oriented so you couldn’t just do it and think about what the solution was, you had to almost do it 2 or 3 times to get the answer and THEN do it.
The storyline was really well written for a mod too, although without voice actors. I personally don’t feel that brought it down though. I think having the next-door neighbor try to voice act for you would have come off much much worse.
I definitely put this on the top of amazing mods. If you want a decent story, more challenging puzzles, and a plot that isn’t pulled down too terribly by horrible voice acting that rips apart most low quality mods, get it.
With that, I also recommend the Portal Flash Map Pack. No storyline, but more of the extremely difficult puzzles and a new boss battle at the end that isn’t the usual Glados battle.