Raiden & Solidus vs. Solid Snake and Big Boss

Fight 1: MGS2 Raiden and Solidus
vs.
MGS1 Solid Snake and "Old" Big Boss.

Fight 2: MGS4 Raiden and Solidus Snake
vs.
Twin Snakes Solid Snake and "Young" (MGS3/MPO) Big Boss.

This is a hard one.

Fight one: Raiden and Solidus would win. Because Big Boss would most likely be killed first. Then they would team up and kill Solid Snake.

Fight Two: Again, Raiden and Solidus would win this one due to their "cyber ninja" feats.