Ok....Riddick is eerily similar to Doom3, if you liked the dark gloom and shadowing of D3....you're going to be right at home in Riddick.
The look and texturing is also close.
Riddick is alittle "dumbed" down in controlls and "in-game" interface due to its consol roots, but nothing too drastic. It does incl. a quick save\load feature
Performace wise I play at 1280x1024 8XAF no-FSAA and its very playable 16x12 gets a mite slow for my tastes. There are tons of video res and ratio options which should cover just about every GFX card \ display combo available.
Also, there is much more "meat" here than in Doom3, story wise...this is a good thing because its SP only. Its an immersive plot and location...all aidded by Vin D's voice to pull you along. In fact....I changed into my "wife-beater" tank and camo fatigues too play hehehe
gotta go....Darkness waits