I've noticed that along with Bitcoin, the earliest altcoins all have relatively low total coin supplies. Bitcoin, Namecoin, Ixcoin, and I0coin all have 21 million coins. Litecoin has 84 million. Peercoin, Primecoin, Tenebrix, and Fairbrix have supplies that are technically unlimited however the rate of inflation is low enough that Peercoin currently only has 22 million coins and Primecoin has about 8 million. I couldn't find any numbers for TBX and FBX but I think they have the same thing going on.
Feathercoin has 336 million total coins - exactly four times Litecoin's supply and Freicoin has 100 million. According to
this article, BBQcoin has a total coin supply of 88 million although I get different numbers elsewhere. Terracoin has 42 million. All four coins were launched after Litecoin.
Then fast forward to late 2013-2014 and suddenly coin supplies start to go up dramatically. Dogecoin has 100 billion and is technically unlimited. Kittehcoin has 100 billion too. Many of the scrypt clones that appeared during this time (e.g. Flappycoin) had very high coin supplies. NXT has 1 billion coins as well as most of its clones. Both NEM and Qora have ~10 billion. Then there are coins like Pennies/CENT and Colossuscoin which had hundreds of billions and sometimes even trillions of coins.
Auroracoin and Darkcoin buck the trend as both only have ~21 million coins. Ethereum and Counterparty also have smaller coin supplies too. Bytecoin has a high-ish supply while Monero's is quite small in comparision so it's really more of a general trend than a strict rule.
Somewhat relevant (notice how many older coins there are between Freicoin and Bitcoin at the bottom of the chart):