Games on Mac have higher requirments?

I was looking at the requirements for games on steam. I saw that for Metro last light the windows requirements are 2GB of ram for both min and reccomended requriements for mac its 8 and 16. For the CPU its saying 3.0ghz quadcore and for mac its a 3.3 or higher quadcore. 

for graphics cards for windows  they reccomend an nvidia gtx 480 for for mac its an nvidia gtx 680.

Why do macs need such insane specs to run a came compared to on a windows computer?

you have to remember that the windows/linux specs are for desktops and the mac for laptops, a mobile chip doesn't compete with it's full size counter part

also many claim mac os isn't geared towards game performance, add in metros poor optimization, and that might explain a some difference

But would that really make the difference for the game needing 8 times as much ram on a mac than on a pc?

I guess if the specs being shown are for a mac laptop that could make up some of the descripency but some of those differences are massive. 

Also the nvidia gtx 480 and 680 are both desktop graphics cards arent they?

Great Answer! I totally did not think about the laptop aspect since I only ever owned powerpc towers makes alot of sense.

I believe this is the right thinking. 

Most Macs sold are either laptops or iMacs. Both of which use very similar parts which are often times slower than their equivalent full sized desktop part. 

Also, if I remember correctly, some of the parts in Macs aren't even equivalent to their counterparts in PC based laptops. They usually, at least for the GPUs, have lower clock speeds or are artificially limited in a way that makes them perform worse. I believe what I read said that a 750M in an iMac only is equivalent to say a 740 or 745M chip in other machines but I could be completely wrong there. 

Also I don't know how efficient the APIs are that OSX uses and with Macs still a relatively small part of the market developers haven't had time to optimize their games for the hardware and OS. 

From just doing some quick searching it seems that many of the minimum requirements are the minimum hardware spec you can get on a Mac. So that may have something to do with it as well. 

The Metro games are a bad example though. They are poorly optimized, 2033 especially, and run like crap even on good hardware and in Windows. 

*680-MX

mobile xtreme

no idea about the ram, unless at that performance range that's the lowest option, but i think they do come with less