To be honest, today, graphics don't play too much of a role in games. There is this sort of "standard" that says that, below this line, graphics are terrible and above it, it's good or great.
Source engine sits right on that line. L4D doesn't have overly great graphics, but it's OK. It doesn't distract game-play in a negative way. If it was a bit worse, then it probably would. At least for me.
CryEngine 3 is, hands down, the best game engine there is at this point in time. Period. There is absolutely no other engine that compares to the specs of CE3. There just isn't. I can see a lot of games being developed on the CE3. It's perfect in every way that matters. Perfection isn't easy to come by, let me say, also. The guys at Crytek have done a brilliant job on that.
But then, people don't expect anything less than perfect from Crytek in the first place. And that's why you're seeing arguments from narrow-minded people like that. It's called the internet. Any idiot can just post some crap somewhere. My suggestion? Ignore them, because they don't matter. At all.
That would be all.
Thanks
Iceman