It would make more sense if he said he was Luke Skywalker.

Making Vader a bit like this guy or this one.

VADER : Obi-Wan never told you what happened to Luke Skywalker. I am Luke Skywalker!

LUKE SKYWALKER : That's not true, that's Impossible!

VADER : Search your feelings you know it to be true.

LUKE REMEMBERS HIS VISION IN THE CAVE AND JUMPS.

Luke was a pupil of Ben's, if he later became Vader that would be before he turned to evil.

Naturally there would have to be some kind of time travel in the Star Wars universe but this is sort of hinted at during Threepio's bath scene in ANH.

If Luke had defeated Vader in ROTJ and took his place Palpatine would have sent him back in time to help his past self take over the Republic.

As Vader saved his younger self this never happened and the Jedi never fell.

Ben and Yoda 'return' physically alive along with all the other Jedi.