FWIW, I thought Watch Dogs was great, but mainly for the campaign, not the free roaming. I liked Aiden Pearce and his story and I thought all the hacking stuff was well done too.
The game was over-hyped and could not live up to the hype, but that does not make it a bad game. I haven't played GTAV, but friends who have say that Watch Dogs does not have the sort of scope for free roaming that GTAV does. Watch Dogs' Chicago has some truly beautiful scenery and feels alive, but if chaos is your thing then hacking steam vents, bollards and traffic lights to cause carnage is quite entertaining as part of the campaign, but not for long beyond that.
The PC port was not great. Ubisoft may have patched it again by now, but for the first few months after it came out, after 45 minutes to an hour of play the game would slow down and skip frames badly. Restarting the game makes it fine again, but this was its worst annoyance for me.