Killzone looked great, but felt mediocre. Didn't get Knack at launch, but have since played it and thought it was a lot of fun. Kind of wish i chose Knack over Killzone for launch, ah well. Contrast and Resogun being launch titles for PS+ on PS4, both games were decent. Resogun more than Contrast, and if Contrast had a Platinum i'd have earned it (got all other trophies mind). Resogun was where the fun was, the high scores between a few friends was competitive over the Christmas period. Thought the game was tough, but fair on the higher difficulties.
Assassin's Creed Black Flag though was a superb title, one of the best Creed games since II. Still think it ranks high up on the list of best Creed titles to this day.
In terms of launch window, infamous Second Son was not a bad game. In fact, one of the better launch window titles. First Light was a good follow up to the game. DriveClub was meant to be a launch game, but delayed to polish it up. Servers literally in meltdown on launch though for this game, and it turned out to be a fantastic racer.