Holmes, of course, is Bruce. Much more Scary Bat-God Bruce than "cheerful Bruce," even though Holmes has his cheerful moments. (Christmas!Holmes, in "The Blue Carbuncle.)
Watson? Alfred. Steady, dedicated, packs heat when needed. Keeps Holmes sane.
Mycroft? Oracle. Not especially mobile, but plugged in to sources of information beyond the ken of average people.
Ace the Bat-hound? Toby. No question. (I suppose you could argue for Watson's bull-pup, but the bull-pup never actually appears; in "A Study in Scarlet," Watson tells Homes he keeps one, and throughout the rest of the stories the dog is never mentioned again. W.S. Baring-Gould hypothesized that the dog chewed on some of Holmes's equipment once too often: "Watson, that dog must go!" But really, it is Toby; Golden Age Ace lives with his master and comes to Batman's aid as needed. What more do you need?)