What people mean by "range" is quite ill defined though, is it the ability to play a variety of different characters with different speech patterns and mannerisms or is it the ability to dramatic, comic, etc roles or even show a wide variety of drama?
Oldman does seem like the natural choice as I think he fits both of those, played a wide variety of characters with different mannerisms, played dramatic roles, played comic roles(albeit not as often but Zorg especially showed good ability). More recently Phenoix would probably be in with a shout as well.
Honestly though I tend to rank the second part more highly, even if an actor does tend towards having the same persona from role to role I don't mind as long as that persona is well suited to them film, someone like Sam Rockwell being a good example of that who shows a lot of range in terms of what he can do with that persona, often in a single role. Brendan Gleeson is also I think very underrated in that fashion, does both comedy and drama extremely well
On the actress side as well I think you tend to get much more of that as well, you don't get as many roles calling for someone to create an entirely different persona. Cate Blanchet does seem like an obvious choice as someone who does drama and comedy very well plus doesn't just stick to a single persona.
