I consider all of these to be pretty good rifles, but I think the category is too broad. Really, to be fair, it should probably be divided into groups like bolt-action rifles, self-loaders, and full-auto (which from this list would only be the Stg 44, I believe).
Obviously, the result is going to be subjective, but here is my list:
Bolt-action:
Type 44 Arisaka Carbine
Very strong action, fold-under bayonet, simple and reliable.
I would have given it to the SMLE Jungle Carbine, which is similarly indestructable and carries twice the ammo. However, the Japanese 6.50x50mm ammo is better than the British. 303 in my view. The Japanese round is easy to fire, with very little recoil, and aims true. Furthermore, it is more than sufficient for the distances that the battles were actually fought. The. 303 is a tried-and-true round, but it is simply too powerful. It forces the troops to carry a heavier round (and therefore fewer rounds) for no real advantage.
Semi-auto:
Garand, by a mile. It's simply a excellent weapon. It was cheap and easy to build, and easy to use to boot. The SVT gets high marks, too, but it is simply not as realiable. No German attempts for a self-loading battle rifle ever made anything realiable or worthwile. They were over-engineered to a point of absurdity.
Auto/Assualt
Sgt 44 by default.