ethereum and bitcoin are still the best. if you decide to buy another coin, then choose coins that have been listed in the top 100 list on the marketcap.
but it would be better if you update the title of your post. became "Best altcoins to invest for 2019"

2018 has been missed, and we still haven't seen an improved market. I think the best investment is now in the crypto option that is in the top market. if you can now have 5 top market assets I think you will get a lot of future profits.

Most users of cryptocurrencies make a choice in favor of the top ten of the top rating of the cryptocurrency market, but nevertheless at this level almost all of them are ethereum. Nevertheless, I would still choose except ethereal and Neo, stellar and EOS. Perhaps even waves that are trying to show good results.

Initially, you need to take the current situation in the cryptocurrency market as an opportunity to invest at competitive prices. But you can not concentrate their funds in one or two altcoin. In any case, you need to take at least ten different coins in your portfolio .

I stopped worrying about my portfolio when I began to invest in the top ten cryptocurrency ratings. Thanks to this, I became more confident in my results.

Well, this is 2019. If you're still looking for the best coin to buy.
I suggest you buy fairc token of faireum.io

Looking at the situation of crypto and Bitcoin markets, it is difficult for us to choose good Altcoins. I can only trade and invest in altcoins on coinmarketcap and wait for Bitcoin goes up and good crypto market to participate.

Below is the list of top 4 coins I mainly focus and the reason why.

Raven Coin
Ravencoin is a peer-to-peer blockchain, handling the efficient creation and transfer of assets from one party to another.

Stellar Lumens
Stellar Lumens is a similar technology to Ripple, however, instead of focusing solely on the banks they have built a system to integrate merchants, banks and the general population.

Historia
A novel idea. To keep current happenings on the blockchain. To ensure that in the future third parties politicians and etc wouldn’t twist facts based on their needs.

Monero (XMR) — privacy enabled by default. There will always be a demand for an anonymous channel for commerce.

The current market looks very good and promising, the top 100 in the coinmarket continues to rise, I'm sure that this month the price of bitcoin can reach $ 10,000, don't think it's impossible because the price of bitcoin has risen by more than 28% in 2 days.