Guerrilla went from making games that did not review greatly on a consistent level (Killzone 2 is the best shooter I've ever played though) and they also did not sell a huge amount. They completely knocked it out the park with Horizon, it's not an apples to apples comparison but having just finished the piece of shit on a disc that is FF15, GG did so well for their first RPG effort. For one, it didn't feel stitched together.
Horizon is such a good base for GG to build on. A horde mode, really flushed out in Horizon 2 will be so fucking fun!