If "Normal" Raiden means his MGS 2 human version with weapons, a case for both sides could be made. Raiden has a disadvantage in durability and striking strength in his MGS 2 version and his base speed is slower, but his combat speed is higher (Subsonic+ vs Superhuman and Hypersonic combat speed) .Because of his reactions I would actually back Raiden if this situation is meant (HF Blade with higher reaction speed is pretty dangerous due to the function of the blade). If he takes a hit as human it is over, but as mentioned his reactions are much better.
If 8-B means MGS4 Raiden or MGR:R beginning Raiden, Arima would be screwed. Raiden could completely dance circles around him and either slice and dice him with his HF Blade or throw him all over Tokyo until Arima is broken (Subsonic+ vs High Hypersonic and Class K Lifting strength)
Mariachi-Raiden automatically wins through ultimate awesomeness and by playing the MGR:R soundtrack
So R1 Raiden more often than not as a human, since he is done if he takes a hit but can fight at higher speed (can't be blitzed, even with lower movement speed). MGS 4 and MGR:R-Beginning Cyborg-Raiden 10/10 since he is to fast, agile and outclasses him physically (Lifting strength is and will be an advantage in combination with his HF-Blade)
R2 10/10 Since he has to be MGR:R Raiden with even higher speed and an awesome soundtrack to boot