You're confusing a few key points. 802.11n can operate on both 2.4 & 5Ghz networks. So while you state speed and range metrics the real question is the quality, capability and environmentals you're, likely, not taking into consideration.
Quality: not all antenna or radios are at all equal. Just because you have an N capable AP means nothing for client connectivity.
Capability: Is your AP MIMO? How many TX & RX? These things matter. Many of Apple's designs for Airport look pretty but are effectively junk for RF performance. This has always been a clear case of aesthetic over function. Many people often buy all in one devices to handle 30�Mbps Internet connections and also lump in 10� wireless and wired devices. These wireless 'enabled' devices are often horrible since they're often underpowered to handle the increased connection speeds as local transfer and Internet speeds increase.
Environmentals: Do you live in a shared living space with lots of neighbors contending for use of channels? Do you live in a 4000+ sqft house and have your AP in the basement? Etc...
TL;DR
I look at this stuff in a lab on a daily basis. This generalization is quite bad.
802.11 b still works pretty well for most people.
802.11 g has better in-house or building range than 802.11 n
802.11 n can be faster. but I haven't notice that being true...ever.
5 Ghz spectrum connections sucks at penetrating walls.