Strength: Ryu cuts jets in half with the Dragon Sword, Ryu.
Speed: Goes without saying, Ryu.
Durability: I don't really know any feats for either one.
Powers: Nihilus by far. He tears whole fleets off the surface of planets with TK, paralyze's powerful Jedi with a gesture while weakened, and can force push a powerful Sith Lord and simultaneously sever her connection with the Force with one hand. He is essentially a Force Demi-God. He even pwned Sion, who is virtually invincible, in like 10 seconds with Force Lightning in cut content.
Reach: Nihilus is pretty big, goes to him.
Range: Nihilus.
Skill: Ryu probably has better actual swordskills, but Nihilus' saberstyle is very easy at switching in and out of saber combat to his preferred style, Force combat, he does this by aggressively using the saber in his right hand, and using Force powers with the other.
Versatility: Hmmm...Ryu, tho not by a whole lot.
Experience: Ryu has more battle experience, but Nihilus has seen more horrors in the Malachor V battle than Ryu could dream of, it is because of that he is a wound in the Force, and he believes all life's purpose is to die.
I say Nihilus 8/10, Ryu can certainly beat Nihilus, but I don't really see it happening very often.
EDIT: Of course he has his Ninpo.
Fine. I'll bring it like this since we think force is instant win. The force only works in the star wars universe. Why because it is the manipulation of medichlorians. Medichlorians is basicly the atom of the star wars universe. The Force users have the ability to manipulate the medichlorians in an object. That is how Strong force weilders severe someone from the force. They use their medichlorians to jam the control or cut the control of the other users from manipulating other medichlorians since that is thing that connect and binds everyone in the universe. Force Drain is draining the medichlorains from another user or an object. There is a book which are canon that further proves this theory when Jedi youngling with their master are out in the forest trainning. Their master ordered them to lift up a creature and move it out of the way because it was dead. Neither the students nor the master was able to remove the creature because it had been completely drained of its medichlorians thus dying. Which led further into the bigger part of the story to find the person who has been trying to drain the force out of others. To Ressurect some dark jedi.
Now relevence. If Ryu Hayabusa is not from the star wars universe and does not have Medichlorians in his body to manipulate. How is Darth Nihilus suppose to use any force powers aginst him? He can't unless its indirectly such as lifting objects and tossing them at the Ryu which Ryu would mainly dodge. Ninpo on the other hand is using Ryu own energy to create his phenomon so his wouldnt be out of whack. Which is why Ryu would most likely pwn Darth Nihilus even with force powers. but the Telekenesis is another thing to worry about.