It depends on the surrondings. It is true though, Snake can't beat them all, but he might have had the advantage on a younger Raiden, due to Raiden being green (although he was naturally talented due to his childhood war days). But obviously if Snake attempts to face off against a superhuman Raiden, he'd lose. He must come up with a battle plan. He can't let himself be seen or he can't enter close quarters on Raiden's account. This is where Snake's arsenal comes in to play.

Well he forced Solidus into his plane, effortlessly. Solidus deflected Snake's bullets saying he was a whole different game from Liquid. Indeed he was, using a highly, mechanically engineered suit to increase his already honed battle skills to allow for inhumane like speed, strength, and endurance. Yeah bullets won't work.

Yep. A single bullet, grenade, or punch would miss due to an electrical
device used to alter the flow of objects that get to close too her. Bullets will miss her, grenades will become inactive, shells would evade her, and I would assume punches and kicks will slide away as well. If blows did work, I'd doubt Snake would try anything stupid due to her carrying that monster of death in her hands. She also had a grudge, Snake was smart to let himself be captured. He could have easily died.

But she did. The only reason why Raiden got out alive was because one of the bullets that was suppose to kill her, ended up injuring Vamp, thus allowed Raiden ample time to escape, while she cry and and morn for someone who can't even die normally. Yeah that is showing real skill right there on Raiden's part.

Bullets won't work on Solidus due to him having deflective arm guards. Also Raiden had a High Frequency Blade, way sharper and deadlier than a bullet from an automatic. That blade can cut through bullets, steel, and of course the soft part of Solidus's suit. Solidus and Raiden were more effective with a blade than Snake. Snake is not a fan of blades, he even said so.

I'm not saying Snake can win against Solidus and Vamp, but he would go in smartly and take the appropriate options when fighting against them. He'd use cover and stealth to his advantage. He'd come armed with everything he could carry. He'd use what ever technology he could to attempt a victory. Simply running up to Solidus or Vamp with no predisposed idea of their skills would definately lead to his death, quick and easy.

Snake is battle smart, he knows that in full close quartered battle with someone of superhuman strength, he'd lose. So he'll have to improvise.

(now)

I'm not saying Snake will beat Raiden, but in order to fight him effectively, he'll have to come armed and prepared for an all out war. Snake knows CQC, so when things get dirty, he'll have to quickly react to Raiden's movements in order to get the upperhand if Raiden manages to closes the gab. Firs things first, he'd have to get that sword away from Raiden.

For most of the fight Snake will be running from cover to cover, trying to find and opening. By using Octocam to his advantage, he'll become one with the environment. But under no circumstances should he approach Raiden's front. He'll have to react to Raiden's movements at all time. Wait for him to slip up. Because if Snake slips up, he'll die.