Most of the Androids doesn't have the correct storage size. Just a few does. Could be a bug or error on formatting the internal storage size.
Give you example. Samsung Galaxy Note 3 - 4.3 - API 18 - 1080x1920 have the 32 GB storage listed. But it showing 4.92 GB storage listed. Actually 8 GB or 5 GB?
Edit: Look like anything that have 4.1.1 have the correct storage size. If I find anything that isn't right then I will report back.
Edit 2: Sony Xperia S - 4.1.1 - API 16 - 720x1280 is good to use. Support up to 4.2.2 apps from the stores. Won't support 4.3 and up though. Must use another one for the 4.3 and up. Unless you have the apk to try out.
Edit 3: Well something isn't right on the Genymotion. Android 4.1.1 saying there is 32 GB or 16 GB or 8 GB storage space. If you look in the apps area then you will see it showing way less than those sizes. Should be showing the same amount of space on both ends. Bluestacks have more space than these. Genymotion only good for testing and playing but not good for a ton of apps save on it.