That is the real flaw with PS+, the games you get free won't always appeal to you or you will already own them. I look at Bioshock Infinite, Remember Me, and Batman Arkham City as great free games, however I already owned them before getting them on PS+. I think the PS3 offerings over the last year or so have been great considering we are paying jack shit for the service.
The PS4 offerings haven't been amazing, but what do you expect when the console just released? They aren't giving us retail games that are still pulling in $60 just yet. We are mostly getting indie games at the moment, but that is alright with me because they have been good indie games and not shovelware. I am enjoying Don't Starve, Steamworld Dig, and Merc Kings. Dead Nation, yes we already got it, but it still has some improvements in this release and its free so not a bad choice either.
Give it a couple of months and I guarantee we see things like Killzone: Shadowfall or other early releases appear on PS+, even if it just the multiplayer.
Did you ever stop to think, maybe the games we've been getting have been too good? Maybe Sony has been too good to us already, and now when we get a game we've never heard of, or thats only $10, or under 80 on metacritic we feel ripped off.