For people that seem to be confused, I'll enlighten you.
You make a trilogy because doing so allows you to make two more products that would be very mediocre on their own but will sell based solely on the strength of the original. Hollywood used to just do sequels, but the problem was that they often only got one extra movie ticket out of that (as part 2 is often really bad). But then they realized that they could make the sequel a bit longer, cut it into two movies, and have the "part 2" ending be a *huge* cliffhanger so that you basically had to see part 3. That way they sell *two* more tickets, even if both sequels are awful (see: Pirates, the Matrix, etc). See how this works?
The same thing is happening with games right now, and it's a bad thing, because it's making the overly ham-handed, stupid plotline of your average game even more predictable, which was something I hadn't previously believed was possible.
- J