BF3's Frostbite 2 engine isn't anything spectacular, but they took a lot of strong features from all kinds of engines, and finally brought everything into a single package. It's not really doing anything new, like with its lighting effects, or destructible terrain, or physics, or any of that... but what's new is that it's finally an engine that does everything in a passable fashion.
BF3 itself, suffers from a boring setting. As strong as the engine is, it's really hard to bring out that "wow factor", when your game is mostly in an ugly desert setting, using various shades of grey and brown. And yet, there's still enough places where I think to myself "Wow, that looked really good".
For me, BF3 was the obvious choice.
Crysis is about 4 years old now, and still has better graphics than almost any new game out there... especially with user created mods. I used to have a few that enhanced effects such as lighting, and improved textures, on what was an already ridiculously good looking game, and recall a few friends giving "holy ***" reactions to just how great things looked.
Crysis 2 actually has a LOT of setbacks from the first. Lower res textures, worse volumetric lighting, less deformable terrain, and inferior particle effects, just for starters. Soooo..... yeah.