As said above, the GPU will be the more important component for Far Cry 3. As for which CPU is better, the i5 is overclockable and will fare better in games that can use more than 2 cores eg. Battlefield 3 Multiplayer. The i3 2100 can't be overclocked, but will do better in games that only use 1 or 2 cores if you have sufficient graphics hardware to cause your games to become CPU bound. For the vast majority of games though, you will be GPU bound and it won't make a huge difference which of those two CPUs you have. Either chip will keep up with today's graphics cards.
The i3 might be the better choice if you aren't playing anything that is very CPU heavy. If you are playing 64 player Battlefield 3 maps or other games that really like quad cores, the i5 760 might be worth the extra money. If all your games are GPU bound, even on a GTX 680/7970, might as well get the i3 and save a bit of money.
Im having these options i3 2100 H61 kit at 150$
i5 760 kit -175$
Considering I5 si Quad and OC-able(but im not goin to try it soon), But i3 is very nicely optiised for FC3 and lots of games, which do yo uthink will be more future proof?
i5 760 the i5 is more for gamers who do not have the $$$ for i7 but the i3 can do all games but on the lowest G
i have an i5 2320 and its works graet but if it runs COD BO1 in MP when it loads a map if you do not have good cooling and if it loads a map the goes 181oF or 82oC playing it goes back down to 160oF i like to use oF but, other then that, it has been working graet.
With a good overclock the i5 will be much better almost universally but at stock the i3 is better (in around 9 out of 10 new games) except in games that really need 4 cores (most games can use them but few really need them) like large multiplayer games.