I would like to argue Halo vs Star Wars because I don't know much about Terminator, Alien Vs Predator, StarCraft, or 40k (I'm biased towards Halo, BTW)
Star Wars had Death Star which destroys planets....Death Stars are destoyed with one well place shot. Even though it is nearly impossible to hit the spot, I'm pretty sure under enough fire, the Death Star would blow up, especially if it's under plasma fire, because Plasma melts away metal, unlike the projectiles used in Star Wars Weapons. Another con is time, the Death Star takes a long time to make, and takes a long time to move into position.
Some people have forgotten that the Covenant also has their own planet destroying methods, glassing. The Covenant uses their huge fleet to completely destroy a planet by unleashing a rain of hot plasma. You can't easily destroy an entire Covenant fleet, you can't easily stop a Covenant fleet from reaching the planet, and unlike the Death Star, moves very fast.
Star Wars has Jedi and Sith, straying from the story to say that there is somehow a lot of Jedi and a lot of Sith, then Star Wars pretty much can win...on land, but just like in Halo, the planetside battles don't matter when you have to retreat because the battle in Space failed and the Covenant have set up to begin glassing the planet.
THe infinite army wouldn't be very useful if they can't win in space, the Covenant are experts in space battles and they have superior shields and superior firepower, the clones don't stand a chance.
Then if the Covenant were to stumble onto Kamino (seeing on how the Covenant always seem to accidentally find the key planet) then the infinite army is pretty much dead.
Just my opinion, if the Covenant weren't so religious they could easily win the war against the humans, because of their superiority in space.