Sean Connery, George Lazenby, Roger Moore, Timothy Dalton, Pierce Brosnan and Daniel Craig are the actors who've appeared in the 'official' series.
If your 'big argument' centres around the other actors who've played Bond, you'll have to include David Niven in the 1967 version of Casino Royale. If you include US TV performances, the first actor to play Bond was Barry Nelson in 1954. If you need to include (South African) radio, you'll even have to include Bob Holness!
http://en.wikipedia.org/wiki/James_Bond
Chris