My personal opinion is that the Syrians are the more potential threat.
In respect to the other countries, the Syrians have the shortest route into the land. Even Egypt and Jordan have quite a lot of arid empty desert in most cases that provide a buffer space, if you want to call it that, to act as a time of assembly for the Israel forces. But Syria is only separated by the Golan: even though its just mountain, still it provides the quickest way into Israel. If they especially feel froggy, they can come in through Lebanon.
That and the status of their forces still remain strong. Throw on top of that a still smoldering resentment of the last couple of times they had their hats handed to them, and you do have the makings for a motivated enemy
Kind of serious...Id be a little worried too.