Greatest Dynasties.

"What makes the Hapsburgs great. I always found it fascinating how they were able to expand the scope of their power through marriage. I think they might have gained more territory through that method than through military power. "

This is true.  Take Charles the V (or Carlos I of Espana) for example.  His mother, Juana la Loca, was the daughter of the king of Aragon and the queen of Castile.  His father was the son of the Archduke Maximillian of Austria (and HRE) and Mary of Burgundy.

However, future generations, in an attempt to keep the holdings within the family, married uncles to neices and cousin to cousin.  The result was Carlos II (died 1700 or 1701).  This grotesque creature, aside from being so horribly ugly his first wife fainted dead away at the sight of him, was throughly retarded.  He learned to talk and feed himself by age 10.  Died at 40.  No heirs (surprised?).

I change my mind now, I say the Medici.

What!? No carolingians!? They should be up there as well.

Romanovs are not that influental because they ruled a country that was traditionally considered the backwater of europe. I don't think the tudors were that influental because at the time england had not expanded like it would until succeeding families took over (i.e. the native dynasty died out).

The way I see it. The three great families are caronlingians, Habsburgs, and the Bourbons, in no particular order. Between the Habsburgs and the Bourbons it's too close to call.