long term: bitcoin
short term: every single altcoin

you can check out the price history of each of them to see. bitcoin will rise in long term. if it is X dollar today it will be worth at least 3X dollar in a year from now.

on the other hand altcoins that are X right now will be X/2 in a year from now at least. but in short term like 1 week or in some case even in 1 day they can go from X to 100X and then fall down to X/2 which is why they are good for short term investment because they are purely pump and dumps.