well for me it was RE3 not because it was tough but because two problems i had with my (*ahem)version
1. it was in chinese(or japanese lol) made it a lil harder to figure out clues and stuff
2. the save option was currupt so as soon as i close the game i lost all the progress so i had to start from the begining everytime. and constant power cuts didn't help much, whenever i got a lil ahead wham.. and my sys reboots ahh i remember now thats when i dumped the UPS in the trash
Took me 2 yrs(lol) to finish the game like this and now I can finish the game in less than 1 hr and 15 mins flat start to finish
still play that when i have had too much of blind/tactical shooters
As for the FPS i would say I find the Quake 3 and similar types harder as you need to use your skill more as compared to the normal fps like max payne fear and everything like that as in these games it is easier to figure out a pattern and work according to that .....
Having said that I haven't played farcry yet (will play that soon considering the popularity here) and may have to eat my words after that but I doubt it.
Leo