As Vlad and Sidi have said, it depends on the market and the size of the client. If your client is a massive multi-national (e.g. Coca Cola), you are very unlikely to get exposure to even a country-level CEO, let alone the global CEO.
On the other hand, with smaller/national clients, exposure to C-suite is much easier to get, even in developed markets. In my first 3 months on the job, I was present and at points helping facilitate a workshop with the COO of a major utilities company in the UK.
As an additional point, while of course exposure to a CEO is exciting, I think much of the value in consulting for a junior is actually from the level of responsibility you will have with more junior clients. In my opinion, it's more valuable to be able to regularly present and lead meetings with the deputy head of Finance (something you could realistically do after 1-1.5 years) vs. attending meetings/occassionally present findings to a CxO.