How far back is still modern? Of guys who are currently active (but talking about when they were in their primes, of course): Hopkins, Floyd, Pac, Jones, Holyfield...probably a few more.
That being the case, I'd say quite a few. Some ridiculously great guys were kicking around in these past 3 decades. Leonard, Whitaker, Chavez, Spinks, Tyson, Lewis, etc. There's been plenty who would have the talent, skill, and mindset to do so. The interesting bit, of course, would be changes in rules (pre-20's kind of stuff), and the boxing environment. How much more or less great would a Mayweather or De La Hoya be if they're fighting about once every other week?
Julio Cesar Chavez, Sr. Particularly as it pertains to fighting on the far more active schedules old-timers did. Floyd would be great in any era, but how much would his hands become a problem for him?
Great? Hmmm. Juan Manuel Marquez would have been greater in an earlier era IMO. Holyfield. Drop that boy anywhere anywhen and he will box his way to, or near, the top of any division he can fit into. Morales, Barrera and Pacquiao have the right stuff I think. Hopkins. Whitaker. I have concerns over the hands of Jones and Mayweather.
Floyd, Pac, De La Hoya, Mosley, Hopkins, Jones Jr, Marquez, Barrera, Morales, Lewis, Wlad. Each of them guys would be great in pretty much any era you drop them in. I treat the current era as post Jones so I've just put him in as a boundary marker. Many of todays stars are weight jumpers so I imagine at any point in history they'd find a weight they could be great in.
