Lewis wins, no doubt in my mind. Tyson always had trouble with guys 6'4" and taller. Tyson looked pretty ordinary against guys like Mitch Green, Tucker, Bonecrusher Smith, and got beat up pretty bad and knocked out by Douglas.

And Lennox Lewis was always the smarter boxer with higher ring IQ. I can't find the clip now on youtube, but I remember watching some random clip that trainers saw Lewis and Tyson sparring in the early 80s as amateurs and Tyson had the edge in the early goings and then Lewis adapted and whipped him. A prime and motivated Lewis? I say he adapts and then whips Tyson, I say late round KO.