For me, it was mainly the length. The story really starts to come into its own, gets really intriguing, and then, credits roll.
I bought it back when it launched, and I loved it, to be honest. Beautiful graphics and great atmosphere, and I really enjoyed the gunplay and the various locations throughout the story were really cool.
It didn't hurt that I got to play it at E3 the year before it came out, and so I knew what to expect, and what I was getting, so I didn't have crazy hype or expectations for it. I just knew that I loved the setting, and the gunplay was fun.
It's unfortunate that it released at a time where expectations for what was "next gen" were sky high, and the game is just a straight forward 3rd person shooter with pretty graphics. It wasn't revolutionizing anything, and wasn't trying to "redefine the genre," it was just a cool 3PS with werewolves and shit.