The way I see things, there are two kinds of reboots. In continuity, and out of continuity. Predators is an in continuity reboot of the Predator franchise; it takes place in the same universe but it spins off in its own direction while reimagining and reinterpreting concepts from the original films. The Amazing Spider-Man is an out of continuity reboot of Raimi's Spider-Man trilogy; it uses the same characters in an entirely separate story and completely reinvents the world from the ground up.
I see Jurassic Park IV being more of a Predators than a The Amazing Spider-Man.