Let me show you.
Assassin's Creed Revelations introduces some excellent tweaks and new ideas into the franchise's formula. I captured some of the best today from my PlayStation 3 copy of the game.
Check out the improved climbing, the better sites, the versatile new hookblade, the intensified action, the expanded assassin-training system and the two best new things in the game: 1) the surprisingly excellent bomb system and 2) the radical gameplay shift for the game's modern-day Desmond sequences.
I compressed it into 11 minutes (some compression, huh?). And I didn't even get to multiplayer. Or den defense. or other cool stuff. Give the video a look and you can see for yourself how much they've changed in this new game.
(The Desmond stuff is at the end, if you don't want to be spoiled. I warn you before it starts.)