This "debate" has been had many times. This site is full of Halo fanboys who refuse to accept the truth. Star Wars would win though, not easily of course, but they would win. The Covenant and UNSC would be easily wiped out by a fleet of Star Destroyers. Star Wars shielding and weapons technology is far greater than that of the Covenant or UNSC. The Flood could be quite a challenge, but would ultimately be wiped out by trillions of droids, billions of those created solely for war. The Forerunners and Precurosrs would be difficult to defeat, their shielding and weapons technology is probably on par with that of Star Wars. Star Wars has a lot of devastating super weapons (not just talking about the Death Stars, there are weapons far more deadly), and also have species such as the Yuuzhan Vong. Halo would ultimately lose, even firing the Halo rings would make them lose, because the Star Wars universe is full of as many droids as there are living life forms.