Without Caesar Octavius would be a non-entity. (He was adopted by Caesar, remember?)
But this is irrelevant to an assessment of their personal qualities and achievements. You might as well say that without Mr Bonaparte Sr, little Napoleon would never have gone on to achieve what he did, so old man Bonaparte was a great general. Or Origen would never have written his works of genius if he hadn't had a rich patron, Ambrosius, to commission them - but that doesn't make Ambrosius a greater theologian than Origen!
If you had some good reason for saying that Caesar adopted Octavius specifically because he recognised Octavius' incredible ability and could predict what a good emperor he would be, then you might have an additional reason for rating Caesar highly (although that would not, in itself, be a reason for rating Caesar over Octavius - a man who recognises genius in another is doing well, but it doesn't make him a greater genius). Alternatively, if you had some good reason for saying that Octavius' brilliance somehow came about because of Caesar's adoption of him (perhaps Caesar mentored him and taught him how to be brilliant) then you might have a better case. Simply saying that Caesar was a necessary condition for Octavius, however, is no case.