OK, so the single player campaign isn't that great, it does have its moments (fighting the scarab) but it's pretty short and many of the levels are similar so it gets a bit repetative.
Multiplayer however is a diffrent story, anything can happen online! and there are endless possibilities for fan created games with the forge tool. You can never really predict what your enemy are going to do with all the tools at their disposal. Stick with the game through the beginner ranks and you will soon find yourself up against opponents who are skillful and smart, this is where the real fun is.