Different phones advertise different total disk space. When you get a brand new phone with Android 2.3.3 and its default apps, how much disk space do those take?
It's going to depend on the device. Each carrier/manufacturer likes to add their own apps and widgets. Some even pre-load multimedia files for you. So, this question really can't be answered. (Most definitive answer would be to just get the file sizes of the stock Android ROMs.)