Okay, so I've been out for a while, I'll try and catch up with what has been said:
Sephiroth vs Vergil: While yes, DMC4 was out before the DB was released, the Vergil campaign acts as a prequel to the manga before DMC3. Therefore, Vergil would still be 7-A since DMC5 wasn't out yet. While you technically can fight DMC4 Dante, who is 3-A, in that campaign, the fight isn't canon and it's similar to how 7-A Nero "beat" Dante in their fight: he ultimately did nothing and Dante isn't trying at all. So Sephiroth still hits way harder, is way faster, and has much more hax. So the fight is still Right, Decent.
Master Chief vs Doomguy: This is "at the time" because Doom 2016 and Halo 4 weren't out yet, it was Halo 3 MC and Original DG (Doom 3 excluded) with full arsenals for both. While DG can run faster, Chief can react as fast as him, his shields can take a BFG blast, his Bubble Shield can take anything DG has, and he's a much more tactical fighter. I think it would be dragged out, but it should still be right given the circumstances.
Roronoa Zoro vs Erza Scarlet: Again, it was "at the time" because Fairy Tail didn't have Deus Sama happen yet and One Piece was in the middle of Whole Cake. Because of that, both are MHS+ and have similar stamina. Erza does hit 6 times harder currently (2.02 Gigatons vs 383 Megatons), but I believe Zoro's Precog, Armament Haki ignoring durability, better training, and Zoro possibly getting upgraded to High 7-A (
here ), I believe Zoro would have a difficult time, but would ultimately win.
@Puas: While I fully acknowledge that by our standards The Meta would ultimately win, considering the DB had several key Rooster Teeth members making the episode, the fact that no actual math was done, and the reason they gave for victory was "Carolina and Church are better friends, that's why," it made the episode basically Word of God and therefore gets the 0 spot.
I'll do a full breakdown of Eggman vs Wily later