I'd recommend Game of Thrones, my #1 series on the list.
Next I'd go with Arrow if you're into superhero shit (no shit like spiderman tho). It's cool, has plots and is fun to watch. It does have some boring moments, when they just repeat and repeat and you just wish the story would continue but its aight, because the plots just get to you unexpectedly and you just end up watching the whole season. The real kick starts at the end of each season though, that's when things get real messy and interesting.
Vikings is next on the list if you're into history.
House M.D if you're into medical shit but you probably already watched that.
That's about it, I think.