I don't think that ATOM can be top 3 coin that is too far to reach that position, and if you ask me which altcoin is the best.. definitely is ethereum.
There's a big hype with ATOM and the price is going down as I can see in the market. This is not a real steel that Atom won the heart of the crowd against Zues, and we know ETH still the king of all altcoins because even bnb and xrp can't beat that one. I hold more ETH, and its going to be more worth it soon.