I would say that Vitali is slightly better than Rafa but JMM is much better than Wlad and he's the better Klitschko so Marquez bros. 1. JMM by a lot 2. Wlad 3. Vitali 4. Rafa
Klitschko easily. Marquez bros are better at getting hit and being exciting but not better fighters, sorry.
The Marquez brothers by a rather wide margin. Both Juan Manuel and Rafael have better resumes than either Klitschko brother. I'd take that any day over loads of title defenses and numerical accomplishments racked up against really sub-par opposition historically for the heavyweight division.