The simple answer to this question is resources and territory. Russia covers nearly one sixth the land surface of the Earth, and is rich with minerals, oil and other resources necessary for expansion and empire.
Russia is also geographically blessed in that its vast territories are unconquerable without the use of nuclear weapons. Ask Napoleon and Hitler how their efforts at invading Russia turned out.
Poland, on the other hand, is sandwiched in between Germany and Russia, and has served as a natural invasion route for Mongols, Huns, Russians, Nazi Germany and later the Soviets, among others. Therefore its very existence as a nation was frequently threatened as it was swallowed by armies and empires from each direction. It also has far fewer resources, and a much smaller population than its powerful eastern neighbor.
One could also argue that Russia emerged as a world power due to leadership on the part of 19th century Czars, whereas Poland has suffered from centuries of misrule and conquest.