How can you tell if a market cap value is too much for a certain coin? I understand that there are coins where there are great number of circulating supply, but why can't they reach trillions in market cap?
You can invest a trillion dollar and force those coins to reach those valuation, i want to see Doge to reach a million dollar one day 
. If you could attract investors in a particular coin then it will reach a trillion dollars.Ethereum is an altcoin and its price won't be higher than bitcoin, never. The possibility for Ethereum price to touch $100,000 is very low but there is a very small prob that it might happen. I don't believe in it but you can consider the related price of bitcoin. If Ethereum gets a price $100,000, what price bitcoin will have in that day? $1,000,000 for one bitcoin.
So you think there is small probability that the price of ETH could reach a valuation that is insane and that too with a coin that has no limit on the number of coins in circulation, may be the government is printing out trillions to match these demands of coins that can be minted in unlimited numbers and some expect the price to rally like a limited circulation coin 
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