Patient, mindful exploration.  That's what I'm about.  While there are many others, my point-of-entry into a video game is in exploring the virtual construct.  No, I don't explore in order to accumulate and obsess over number-crunching armor and weapons stats, and I don't explore for the sake of breaking the game and seeing what the developers let slip through the cracks.  But there's an inherent need in me as a player to completely engage my ocular senses within a game world ... and to simply see all that I can see.  If the developers want to mercilessly wrap me around their little finger, they only need to throw in some hidden items to collect, and the completionist switch in my brain is also engaged. 

Assassin's Creed is indeed satiating my bent for exploration.  The Crusader-era re-creations of the Holy Land will drop your jaw.  The urban constructs are pieced together with artfully-restrained hands.  The surroundings achieve a hallowed magnificence, or a subdued pallor, all with meticulous attention to detail. 

And as I take Altair, the protagonist, on, around, and above those hobbled streets, the meandering populace is not always indifferent to my presence.  The crowd forms into a collective character in and of itself, putting the towns' heroes and villains on a pedestal, or burying them behind blurred, obscure masks.  The wealth of the robes or the wrinkles in the rags the people wear embellish the surroundings, telling the people's stories in thread counts rather than word counts.

And free-walking 10, 20, and 30 feet above everyone's head in Masyaf (where the Assassins are headquartered) is every bit as thrilling as swinging Peter Parker through Spider-Man 3's Manhattan Island.  Exploring the mechanics of Altair's fluidity matches the impressively-calculated movements of a Sam Fisher inching through a Splinter Cell.  And pulling off a high-speed evasion or blending seamlessly with the local denizens is worth its weight in Hitman gold.
And this is just tip of the iceberg stuff.  Doubtless there's plenty more in store.  But if it's patient, mindful exploration that gets you through the door of a game, then Assassin's Creed has got your ticket in.