Age of Empires III has the sweetest graphic ever

That's not the point. The point is that ever major game, including Halo 2, Half-Life 2, Killzone 2, Elder Scrolls 4, etc. all use this same engine.
didnt we alredy know this... You would have to live in a closet to not know it

most games dont use the exact engine... They modify it they way they see fit...
By looking at this list, I can say that about 60% of the games I play use the Havok engine. Must be a pretty sweet engine.
An extremely good example of such a game with a Physics Engine would be Flight Simulator. They may not use the Havok engine, but they will need a pretty damn good one.
Basically, this is what keeps objects falling at a steady -9.8m/s[sup]2[/sup] and collision crashes and many of those things. It's what makes the game realistic even though they will most probably change a whole lot of values.
Car racing games are another extremely good example, just steer your Ferrari into another car and try to record speed, mass and everything related. Then put those values into Physics and you will have a very similar result as to the in-game crash.
the one thing I am in awe about this program is that how many people did it take to make... there are SOOO many possibilities of different materials to make. Glass shattering, Wood Plank falling, Gun Shells Falling, Waterfalls... So many things to mess around with... How could they even figure it out
Actually, there a big flaw in the engine. Anything that weighs more than, a ton I think, has the same physics of something less than that. A 200 ton airplane obeys the same physics as a two pount rock.
there's also meqon or w/e physics engine, Duke Nukem Forever is supposed to use it...
It's still a very nice engine. I wish I could afford it...