Personally I think CanYouRunIt is actually a bit shit. It can be a good inidcator, but if you fail just one thing it can fuck up your whole score, even if you beat each other requirement by shitloads.
For example, here's mine:
That's bullshit. I barely pass the minimum requirements? The only thing I failed was that I have a dual core and not a quad core processor.
If I use YouGamers' Game-O-Meter then I get awesome results. Which tbh, I'm kinda expecting, my processor really is the only thing that I'm losing out on. In the graphics department, I have 320MB of dedicated video RAM, add in shared RAM and it brings the total up to 2GB of video RAM.
And of course I have 4GB of main RAM on a 64bit OS so I'll be able to make full use of all of it.
Look how far ahead my PC now is from (1) the minimum and (2) the recommended specs.
Neither tests are flawless. But seeing as YouGamers' is based on 3DMark 06' then I kinda trust it more. That said, I don't really expect to play GTA IV on maximum settings because I am aware my hardware isn't the greatest anymore, but I still expect the settings to be pretty high.