I would say witcher if you actually finish those games.. crysis if you want the awe this#$#$ is awsome looking factor 
Heres my perspective.. after FF8 bugged on the third disk (pc) i havent finished a game since... Ive never played the single player campaign on wc3.. nothing. When i play games i play with others.. i get on vent and talk to some friends.. or i go play some tf2 and frag with some friends.. Farcry had a ok multiplayer(nothing special balance/competive side wasnt on par with the big names).. but it wasnt anything special. So in that respect you may have more fun with the witcher first, since crysis is basically the same game type..... Personally ill buy crysis on release day install it and go into the multiplayer and start killing players
As others have said its a FPS. if you like that type play it.. I buy everything i want because its my relaxation. but as you can see i A.D.D my gaming so maybe im not one to ask
.
average day:
wake up
eat
work
eat
work
tf2/ cs:s
dota
wow raid <hellgate london has taken this place
dota
DoD / tf2 /cs:S
movie
movie -movie with special someone
"fun time" with the special someone, prolly not because i ran out of prepayed time or incompatible game type.......
rinse repeat

Heres my perspective.. after FF8 bugged on the third disk (pc) i havent finished a game since... Ive never played the single player campaign on wc3.. nothing. When i play games i play with others.. i get on vent and talk to some friends.. or i go play some tf2 and frag with some friends.. Farcry had a ok multiplayer(nothing special balance/competive side wasnt on par with the big names).. but it wasnt anything special. So in that respect you may have more fun with the witcher first, since crysis is basically the same game type..... Personally ill buy crysis on release day install it and go into the multiplayer and start killing players
average day:
wake up
eat
work
eat
work
tf2/ cs:s
dota
wow raid <hellgate london has taken this place
dota
DoD / tf2 /cs:S
movie
movie -movie with special someone
"fun time" with the special someone, prolly not because i ran out of prepayed time or incompatible game type.......
rinse repeat