Here's my team, without (hopefully) anyone too OP:

The Swordsman: Link - Legend of Zelda. With either the Master Sword or the Biggoron Sword. The Bowman: Hanzo - Overwatch. The man bow, samurai commando. The Ax/Hammer: Yuno Gasai - Future Diary. She is scary good at killing things. Just convince her that Sauron has Yuki. The Wizard: Terra Branford - Final Fantasy 6. She decides to be human at the end so still mortal. Comic Relief: Kronk - Emperor's New Groove and any character from Anchorman. Maybe Brick Tamland since he can also summon deadly weapons from nowhere Ringbearer: Shepard - Mass Effect. She withstood Reaper indoctrination and is a capable warrior. Ringbearer's Sidekick: Garrus. I mean who else? The Betrayer: This is a tough one, so many possible choices. I'll go with Loghain from Dragon Age: Origins. Just like Boromir, he has honor, so he'd join the Fellowship in the first place, but would ultimately try to take the Ring for himself when it told him it could help Ferelden beat back Orlais.

I think they can pull it off. They're all great fighters, many of them have advanced weaponry that'd help out a lot, and besides Loghain (and Yuno if she saw through the lie) are good-hearted/honorable/compliant enough to see the mission through.