I bought the game for the PS3 and beat it about a week and a half later (I got a platinum trophy too!). For all intents and purposes it was better than the original. However, it wasn't as good when you consider the time period in which both titles were released .
In 2007, when the original game came out, we really didn't know what to expect out of new consoles, and Assassins Creed delivered a "next-gen" experience. Sure some quests were repetitive, but the story was solid and the graphics/decals were awesome. Now in late 2009 we have experienced so many great games on the consoles and PC since the release of the original game. In fact, I started Assassins Creed 2 immediately after I had finished (got a platinum) in Uncharted 2. I couldn't believe how bad the faces and animation were in the new Assassins Creed 2, I even thought my PS3 was bugging out. I eventually realized that Uncharted 2 simply had facial animation and graphics that are pretty much unmatched on any platform.
Assassins Creed 2 is still a good game and I would recommend it if you enjoyed the first one.