Q4 looked like Doom3 with the lights turned on. the way the vehicles and some of the gameplay... is slightly similar to HALO.
I love FEARs eye candy, up until like halfway I spent most of the time shooting things and looking around.
IMHO
Doom3= good play once game... great game for its time (i pitty those that didnt get to play it with decent 5.1, I suggest 5.1 headphones)
Q4= yes, doom3 with the lights on. yet I could play it maybe once or twice the "transformation" part was quite interesting.
HL2= The vehicle parts drove me crazy and gave me motion sickness. Although those head crab things looked pretty cool.
FEAR= eye candy game. the voices and images did creep me out a little but got quite annoying. the "soldiers" were pretty smart. wish they had a mod to turn off "The Ring" stuff.