I thought Road to Perdition sucked, I've never seen the other 2.
Apparently its a movie you either like or hate. Each time I watch it, I like it more.
The other two, along with the original "Scarface" are dated by today's standards (they're from the early 1930's) but MUST see's for fans of this genre. If nothing else, you'll see great early performances by three great actors (James Cagney, Paul Muni and Edward G. Robinson).