L4D wasn't graphically demanding and since L4D2 is based on the same game engine the results aren't too surprising. When I see numbers like this at resolutions like this, I can't help but wonder what the programming team for Crysis was smoking.
You really cannot compare the Physics in L4D vs. Crysis... Nothing moves in L4D, just the enemies.. The maps in L4D are also very small compared to Crysis. If L4D had the same physics as Crysis, you would not get 150+ frames with xAA enabled....Simple as that....
Crysis came out in 2007, and is still the best looking game to date.
The game didn't even max out the Crysis-engine...and there are plenty of mods that bump the graphics beyond the default-max Very High settings.
Not to mention that Crysis has "actual physics" (youtube 10,000 barrel explosion)...whereas in Left4Dead, most objects don't move...ie. Chairs, tables, and other small objects are basically a part of the map.
Hell, the Crysis engine is so graphically demanding that the Crysis2 engine is actually a downgrade so they can put it on consoles.
You can't compare the respectable Left4Dead engine (maybe a honda civic) with the awe-inspiring Crysis engine (more like a Lexus).