for me
Bitcoin... first to market so other crypto coins have their financial foundation built on it (market dominance 41%), fixed supply @ 21 million (currently only 90% out in circulation), traded on most exchanges thus exchanges will always need to keep a health supply (there was even a shortage of the coin in the last bull run) popular house name... even Grubhub jumped on board and now is given btc rewards for orders
Ethereum ... fantastic platform to develop on and to create more financial assets, so good that binance down right copied it minus the security level. ERC 20 concept was incredible, about 250k tokens created over the concept with 40 of them appearing in the top 100 crypto coins. USDT (tether), Binance, chainlink, uniswap. Not happy how they treated miners with the new upgrade and not a fan of their eth validator concept. White paper in 2013 it will reach its 10th bday in 2 yrs. I also think the Play2earn concept is going to be huge as seen with its rise in the asian markets.
wild card Monero
This is what decentralized is all about, its so dam sexy that US goverment hates it. It states that its to private and drug and sex trafficker's utilize it, on that basis i guess we should also make the US currency illegal. China hates it due to the fact that large mining farms arent a dominating force and its asic resistant. Cryponight algo is also much easier to process than the two previous mentioned which also means less power required to process the blockchain.