This may sound trite but my favorite was AC1. I was so pumped for it, preordered the special edition with the metal case and figurine, and then really liked Altair as a character.
I got hooked on PC gaming when I saw the back of the box for Baldur's Gate 1. When I saw it, I knew I wanted to play that game. JRPG's just were not my preferred RPG choice and I wanted something more Western and I saw that it was possible via PC gaming.
I am one of those people that need to wait until the game to really create a backstory. I'll play a bit with the stats but if I make the backstory, I will start to get way too eager for it.
I am most excited for the exploration of the city and its inhabitants. I look forward to getting lost and spending way too much time enjoying the atmosphere and ignoring the main story - which I definitely intend to enjoy - but I love the world building that CD Project Red has consistently provided.