I'm going to let you in on a little secret. Phoenix Wright: Ace Attorney isn't a game. It's a book.
When you think about it for a second, it makes sense. A fictional mystery book has, by definition, a protagonist investigating a crime committed by one of several prime suspects. The book usually provides information only the protagonist is privy to, with perhaps a little nugget that is only given to the reader--usually a misleading one. The protagonist gathers relevant evidence to piece together exactly what happened, following a trail of clues and getting leads by speaking with various other characters. These other characters, as Brad also described, are not black-and-white, but many shades of grey to ensure the reader is never quite sure of their motivation. Because of the physical nature of books, there is only one conclusion which is reached by reading the novel all the way to the end. There is only one path the reader can follow, the path laid out by the novelist.
This is exactly how Phoenix Wright functions, to the letter.
Brad gave the secret away in his review. He never spoke about gameplay, or graphics, or inventory systems. The main praise he gave to the game was directed at aspects more associated with literary works, such as the writing and the cast of characters. While these are important for many games, particularly role-playing games, it's rarely at the forefront of any game to the extent it is here. Brad's only mistake was likening it to a point-and-click game.
While many comparisons can be made to the genre, in Phoenix Wright's case it is a misnomer. In a point-and-click game, the protagonist is usually visible, and is either under direct control or guided within a confined space. Here, in everything except for a couple of courtroom cutscenes, Phoenix Wright himself is never seen. Each scenario and location is presented from a first-person perspective and like a descriptive novel, but pictorially rather than textually. In fact, hit the "examine" command and the game gives the description to non-important objects through Phoenix's observation through descriptive writing, just like a novel would.
But, you say, what about a title like Shadowgate? The game is entirely based upon descriptions, and first-person still scenes with simple commands to control the character. Again, Brad has me covered. As he pointed out, it's impossible to leave a vital clue behind. Phoenix never goes into the courtroom without the right piece of evidence, and there are no red herrings. There is no backtracking once Phoenix has completed one phase of the story (Phoenix Wright even calls them "chapters"!), be it investigation or courtroom. As such, it's utterly linear; the player follows a trail of breadcrumbs during the whole experience.
Thankfully, the trail is very interesting. I, again like Brad, found the characters very engaging, and like the evidence, all of them have a function in the plot. From the obsequious hotel bellhop to the Yakuza-connected television producer, each one is a real person. Characters never feel two-dimensional, displaying emotional awareness I'm not used to seeing in games. Everybody is a suspect (even myself for a time!), and nothing is as it seems. Just like a good book.
I will agree with Brad that sometimes the game's logic is obtuse at times, but nothing that requires a walkthrough. In fact, if something's really stumping you in court, trial-and-error (no pun intended) will get you out of a spot eventually.
With what defines a "game" becoming more ambiguous, it is refreshing to see more titles thinking outside the box. While Phoenix Wright: Ace Attorney can be faulted for not having conventional features such as multiple endings or non-linear paths, it is for these same reasons that it succeeds. The replay value of the game is as good as its stories. Fortunately, it's a game that's worth re-reading.