NyxSlayer has a good idea, try playing a few other games and see if they slow down as well, install a game on 1 harddrive and another game on another harddrive, you will find out if its a harddrive issue or a different issue.
update all your drivers
Run a virus scan
Run command prompt as admin and type "CHKDSK /f" of the drive that your games are installed on
make sure nothing is overheating (clean out dust)
I guess you rig is not helping at all, as you might know Crysis 3 is the game with the best graphics so far... Do you play another video game like Battlefield 2/3?? any game where you can compare the FPS ??
NyxSlayer has a good idea, try playing a few other games and see if they slow down as well, install a game on 1 harddrive and another game on another harddrive, you will find out if its a harddrive issue or a different issue.
Another issue could be the temperature, I mean global warming does not only affects the enviroment, but our gaming desktops as well... xD try downloading a GPU monitor though
Ok i have installed the latest tomb raider and Dead space 3 and they both run on full graphics just no AA +- 60 - 70 fps my pc's temp is fine will test installing on diff hdd tonight.
I also saw last night sometimes i can play cry 3 on high with no prob with more demanding environments but then i get to a closed off location and it lagg so much i cant even play on low.
temperature may have somthing to do with it, hardware will slow down almost to a pause if it gets really hot, which will effect game performace, rivatuner or MSI after burner are 2 free overclocking tools that come with an accurate temp monitor.
turn off background services from task manager,,,, And the most important thing .... When playing games, disable your antivirus temporarily.... Install Service Pack 1 .... update your drivers and try also updating your Bios...