Most comic book fanatics have seen this fight time and time again, and it was a dramatic arc even then. Now combine that with the characters the cinematic universe has established and built, this movie is sure to put a VERY BIG dent into the cinematic universe as a whole. What's more threatening than an alien race with little knowledge of our human race? A killer robot who cannot die, coming back stronger and stronger, who was built to protect the human race and therefore knows every efficient way of obliterating it.
It will be better because if you have read the comics Ultron is a basically unstoppable robot that Henry Pim (Ant-Man) created. Ultron can take over any type of technology, meaning Iron-man's suits, Jarvis, S.H.I.E.L.D, any computerized thing. It will have so much action, and if you have seen the trailor it is non stop action.