Depends on the market, but from what I've seen in Japan, a new grad can request marketing placements at companies they're interested in. Getting that slot often boils down to luck, not skill.
If you want a more predictable path, consulting or agency work gives you a clearer route. But if you're aiming to own the creative direction-visuals, copy, the whole concept-you'll need to go through a planner or creative planner role. In Japan that usually means an art/design school background and a portfolio in the hiring process.
as for what separates a top marketer, that's entirely role-dependent. "Marketing" is a massive umbrella term covering vastly different specialities. The bar for excellence shifts completely between, say, a performance analyst and a brand strategist. No one-size-fits-all answer.
