2011 and 2013 don't exactly suffer in terms of quantity, but rather of quality; Killzone 3, Motorstorm: Apocalypse, Uncharted 3, Sly Cooper: Thieves in Time (I don't like the series as a whole, but this one in particular is even worse than 3), God of War Ascension and Gran Turismo 6 were all disappointing and VERY inferior sequels, with a lot of them also straight up bombing.
There are bright spots, sure; LittleBigPlanet 2, Infamous 2, Resistance 3, The Last of Us, Rain and Ratchet & Clank: Into the Nexus, but that's kinda it? The problem is that those years are mostly filled with actual bad to garbage games among the likes of Ratchet & Clank: All 4 One, Beyond: Two Souls, and virtually every PS Move title (as bad as the EyeToy stuff on PS2).
I may be biased for 2007, but a year with Folklore, Everybody's Golf 5, Boku no Natusyasumi 3, Warhawk, Ratchet & Clank Future: Tools of Destruction and Uncharted: Drake's Fortune (which wasn't that good, but it gets points for launching such an important IP)? It's just... *chef's kiss*