Whilst I understand the wish to use the property analogy, it isn't a perfect one for a couple of reasons that I can see.
One, the market is not liquid, there are far more sellers than buyers. If I owned the said manor house I could put it on auction next week and achieve a good high percentage (say 75%+ for arguments sake) of the price I could achieve if I marketed it properly and with patience. The same is true if I held a portfolio of 100 manor houses, I could find a trade buyer in a short time and achieve a good percentage. The same does not hold true of your portfolio of domains (as you have stated yourself in the past).
Secondly, domains are not investments so much as speculation (note both can lead to great profits, but there is a difference). If I bought the said manor house at auction and had absolutely no use for it I could get an income from it quite easily, by renting it out. There exists a ready market for property rental, with no skills required as there are many providers that would do everything for me. The same is true if I bought 100 manor houses. Even if I do not gain income there is a large enough market that I can have a good idea of it's likely sales price at any time, and decide whether to hold or sell. However domains have no such easy route to income, nor a trackable value.
So to extend your analogy somewhat, I think the internet is still in the wild west of property development. Pay a small fee to a local body and you could have your patch of land. If you could afford it there was nothing to stop you buying thousands of patches of land, either directly or on the secondary market. Some registered land that quickly became valuable due to gold or oil making them money very easily (think top end generics in financial industry). Others registered land that became valuable due to their own hard work, farmers or industrialists perhaps (think top brand names). Others again registered land that became valuable over time, purely because that cheap patch of mud ended up in the centre of a city or tourist area. These however became valuable gradually over time and most changed hands many times. This last section is how is how I see most middle level generics. Right now we do not know where the internet "cities" will be. If G (or FB, or whoever comes next) means that holding a generic gives no value whatsoever then you will be holding land in the centre of a desert. If however the custodians of search decree that it becomes more important, then you are going to be a Duke of Westminster. As you cannot know which way it will go (however much you believe it), then fundamentally domain holding is speculation.
All IMHO of course, without a crystal ball it really matters not a jot what any of us think or believe, but interesting none the less.