MCU Iron Man vs MCU Spiderman and Winter Soldier

Civil War armor for Iron Man. Civil War gear for Spiderman and Bucky. In-character, but fighting all out. To the death or incapacitation, starting distance of 15 yards in the same location as the Iron Man vs Cap/Bucky fight.

Who wins and why?

Bucky doesn't have the necessary power set to compete. And Spidey doesn't have the experience or the 'killer'instinct. So IM wins.

As time goes on though, I'm sure a level of parity will begin to become apparent between Spidey and standard gear IM. Spidey will defo be above Cap before long.

Well, depends on whether Iron Man gets any upgrades to his future standard armors. They already kind of hinted at it during that Infinity War preview, when the Russos said that Tony is the one character who is aware of this big future threat (after his apocalyptic vision in AoU) and was prepping for it. Though we should get a better idea of things once Homecoming arrives.

On topic though, as things stand, IM wins.

Depends. If Spidey can web up the repulsors and ground him, the two can take it. Without that though, it's unlikely until we get more feats for Spidey through his movie. Spidey's inexperience at the moment will cripple him. If Cap was able to take advantage of it, IM definitely can.

^Agreed. Iron Man wins currently.