Far Cry 3 is a graphically-demanding game, and entry-level GPUs simply aren't fast enough to achieve playable performance.
Using the game's Low detail preset at 1280x720, the Radeon HD 6450 and GeForce 210 DDR3 are completely insufficient.
With that said, the GeForce GT 630 GDDR5 (otherwise known as the GeForce GTX 440 GDDR5) and Radeon HD 6670 DDR3 do well enough at this entry-level combination of low detail and resolution. But what about at 1920x1080?
As we might have expected, the Radeon 6670 DDR3 and GeForce GT 630 GDDR5 are unable to maintain suitable performance. Consider the GeForce GTX 650 and Radeon HD 7750 bare minimums for playing Far Cry 3 at 1920x1080.