Watch Dogs is a surprisingly demanding game, particularly when you consider the console hardware it's also running on. But at its most entry-level detail settings and a 1280x720 resolution, you can get by with a Radeon R7 240 or GeForce GT 630 GDDR5. At 1920x1080, you want a GeForce GTX 650 or Radeon R7 250X to keep your nose above 30 FPS. But a Radeon R7 260X or GeForce GTX 750 Ti is going to save you from a lot of the stuttering we observed.
Step up to the highest detail levels, though, and you'll want a Radeon R9 270 or GeForce GTX 760 to run at 1080p. At any resolution higher than that, shoot for high-end hardware like the Radeon R9 290 or GeForce GTX 780. Indeed, the best experience we had was with Nvidia's GeForce GTX Titan overclocked to achieve performance similar to a GeForce GTX 780 Ti.
Even with the Ultra detail preset enabled, which you'd think would shift the workload toward graphics, a strong host processor is surprisingly critical. While the Core i3-3220 and FX-4170 only mustered a 24 FPS minimum, the FX-6300 almost hit 30. The FX-8350 and Core i5-3550 managed a more tolerable 37-88 FPS, and Intel's Core i7-3960X lead by not dropping under 51 FPS.
Of course, you can mitigate the performance hit by lowering your detail settings, bringing frame rates back up, but that somewhat defeats the purpose of gaming on a PC. Make sure you have an FX-6000-series CPU at minimum to enjoy Watch Dogs at higher graphics quality settings, but a Core i5 or FX-8000 would be much better. The publisher recommends a Core i7 for the best possible performance, and we have to agree.
As for the game itself, Watch Dogs is a little bit of GTA with a hearty helping of Deus Ex and a dash of Far Cry 3. I wouldn't go so far as to say it's any better than those titles, but if you're into the sandbox genre, I'm sure you'll find something to enjoy. The PC build sells for $60 on Amazon, and Nvidia bundles it with certain GeForce cards.