No, they are not.

Even though they are all based on the blockchain technology and use public key cryptography, there are certain technical aspects that differentiate one from another which add intrinsic value to the blockchain implementation and enables individual investors to make choice based on their personal needs and goals. I am not going to explain some technical aspects of individual cryptocurrencies, like encryption algorithms used, that do not necessarily make any valuable differentiation between the coins.

In no particular order, the differences pertain to

1. Maximum Supply – Unlike fiat money which can be printed at will in unlimited quantities virtually at no cost, the maximum supply of most coins is limited. That means that it is known in advance how many coins can ever be in existence. Common logic suggests that the lower number of coins there can be, the higher the value per individual coin it can possibly reach, but this is not necessarily directly correlated.
2.  Network Hashrate – In simple terms, the amount of time and computing power required for the network to mine a new coin and add it to the supply. Due to designed restrictions baked into the technology, as the time progresses it takes more and more time and computing power to mine new coins. Obviously, it costs money to produce digital coins, unlike fiat money. For example, at the time of writing of this blog, the cost of electricity, computing power and manpower to support it, to produce a single Bitcoin is about $1,000. The network hashrate is estimated in number of tera hashes per second (trillions of hashes per second) the network is performing.  See hashrate charts here
3. Speed – Each blockchain transaction requires multiple confirmations from different distributed nodes in the network, before the transaction record is considered valid. Each coin technology has different requirements for the number of confirmations, and the time needed for a single node to confirm the transaction differs as well. That means that from the moment you initiate the transaction, it may take from a couple of minutes to many hours for the transaction to be confirmed. obviously, this makes some coins to slow to be efficiently used in certain scenarios, like point of sale cases for example. Larger number of confirmations on the other hand increases the integrity of the transaction making certain coins more valuable as the store of value, rather than a daily use coin.
4. Transaction cost – Each blockchain transaction costs something, and the cost is usually calculated as a fraction of a coin. This cost also differs hugely between the coins. Some coins will charge you pennies for high value transactions, others will charge you considerably more.
5. Privacy – Even though many people will assume that the use of cryptographic technology automatically makes cryptocurrency transactions private, it is not so. Transaction records store information, like IP addresses, that can be used to trace the transaction to the parties involved. Actually, at this moment only a few altcoins provide privacy and untraceability.
6. Availablity – You cannot buy any altcoin directly for dollars or euros, unless of course you are dealing directly with a person who possess the digital coin. Most purchases are actually done on some of the exchanges. Some of them allow you to use dollars or euros to buy a only certain coins, and once you acquire them, you can use them as the means to purchase other altcoins. Not all exchanges list all coins either, so you may need to transfer your initial coins to an exchange that lists the altcoin you desire. Once you purchase the desired digital coin, you can keep it in your coin wallet on the exchange, or transfer it to a local wallet running on your desktop or laptop, your smartphone, or even to a hardware wallet, a device specifically designed to securely store your digital coins.
7. Acceptance – Once you posses the digital coins, you can choose to keep them in expectance of the increase in value, or you may need to use them to purchase things other than digital coins. You cannot just walk into any grocery store (at least not yet, but that is the goal) and use just any digital coin to purchase some items. Even the most accepted and well know coins are still not widely accepted in regular stores and businesses. However, that is changing literally on a daily bases. Just few days ago I have seen a real estate listing for a multi million dollar apartment in Trump building in South Florida.