A lot of it depends on the map size. The smaller the map, the fewer the civs there are to beat you to wonders. I usually play on Tiny map (4 civs) cos my computer was made in the stone age. Last game I played I got all the wonders I wanted (i.e. Oracle, Porcelain Tower, Hagia Sophia and a couple of others).
Having said that, getting the Hanging Gardens seems nigh-on impossible.