The original films (especially episodes IV V) are far better executed than the prequels. The story telling, plotting, acting, etc are wildly better than the chewed up nonsense that came later. Just watch the Red Letter Media review. He does the best analysis I’ve ever seen.

Vader was lured from the light to the dark, so it’s not entirely implausible that he could have a moment of redemption. Now, whether or not this was handled well, that’s certainly worth arguing about.