Another problem could be because your running non N devices on a single band router. Some newer routers have dual band N/G/B that allows you to run multiple devices on different bands. Thats why I switched to G only, I have a WiFi printer that is G, an old Laptop that is G, My new Laptop that is N, and my X that is N. Pushing everything onto the same band instead of limiting it is more efficient. When you run any device on a single band WiFi router, it defaults to lowest band automatically, even though it will show "N" on your phone, its running at G speeds. Thats probably causing the issue on most devices.
Now if its dual band, N devices actually run on N.