If Dr. Doom, Lord of Latveria comes into play, does he count for his effect? And if you had a Dr. Doom already in play, does that count? I'm just wondering because my friend was playing like this and i was wondering if that is what happens.

As long as he is a Doom character when he comes into play (it is possible to remove or change his affiliation), then yes, he will count. The old Dr. Doom that you replaced with the 8-drop would not count, however, as it is not on the field when the new Dr. Doom comes into play.