The top 3 cryptocurrencies contenders are as follows:

1. Bitcoin
2. Ethereum
3. Bitcoin Cash

Bitcoin

Known for its domination in the crypto world. It has scalability issues. Lead developers cancelled the segwit2x upgrade which only means that Bitcoin is going to suffer large transaction fees and higher block time. Bitcoin Market cap was at its peak on Nov 5 with 123 Billion as per Coinmarketcap.com but it came down to 108 Billion today. Bitcoin will still remain a leader despite all these since one cannot buy alt coins directly using fiat currency except for Ethereum and Litecoin. Bitcoin is never going to succeed as a payment method because of the higher transaction fees. A single Bitcoin transaction consumes the same amount electricity to power 7 US household in a day. Hence bitcoin will not remain a leader in the future.

Bitcoin Cash

Currently at #3 in the cypto world. It is a hard fork from Bitcoin which occurred in Aug 2017. After the cancellation of segwit2x upgrade many investors seem to have moved over to Bitcoin Cash. Bitcoin Cash went from $600 to $2000 after the news and settled to $1300 for now. Bitcoin Cash supports 8 MB block size and is faster than Bitcoin but it is all the hype which creates the surge. Block time is still 10 minutes and it is very slow compared to Ethereum. And it may see an uptrend only if the support holds. Also there is a news that the Bitcoin Cash mining difficulty was lowered last week which greeted many Bitcoin miners to switch to Bitcoin Cash for profit. So i don't think Bitcoin Cash will stay above $1000 for long.

Ethereum

With a strong hold on #2, it had a stable price of $300 for quite some time unlike other coins in the market. Current market cap is at $30 Billion. Ethereum price is slowly on the rise lately as investors are slowly realizing its potential. Unlike the other two coins, Ethereum is not just a coin but also features smart contract platform. It allows you to create digital tokens which can be used to represent share, assets or proof of membership. With smart contract, one does not require 3rd part to raise funds for your application. And it does not stop at raising fund, you can also get proposals from members and proceed based on majority of inclination. Ethereum block time is 12 seconds whereas the other two takes around 10 minutes. Despite the recent Parity's wallet issue, the price has been steadily increasing. With Casper upgrade aiming to include more security, reduce the risk of centralization and making it more energy efficiency, Ethereum is definitely a buy at the current price $326.

Unlike other Alt coins, you can buy Ethereum directly using fiat currency in Coinbase website (Link below)
https://www.coinbase.com