PC Free Game List

Depends on what you want

I would recommend Guild Wars 2 and Path of Exile.

I have never played DoTA, Warframe and Fortnite as they are not my cup of tea. But people like them.

I have also heard good things from SWOTR , don't buy anything just play every class story. It has good story.

ESO is having a free week, so you can give it a try before buying.