The 23-year-old signed for the Reds in a £4.7million move from Mainz in the summer but missed the start of the season after breaking his hand in a pre-season friendly against Chelsea.
Karius is now fully recovered and is set to make his debut for the Reds in the League Cup game against Derby County on Tuesday night.
Klopp said: "In the moment when we signed him, you can imagine we thought 'he's not too bad' and that's how it is.
"He was a really, really, really strong Bundesliga goalkeeper.
"That means a lot. Germany is a goalkeeper country - we have no issue with goalkeepers. I would say at the moment that the best goalkeeper in the world plays at Bayern Munich, and he's German. We always have good ones, maybe not the best in the world, but always good ones. That's the kind of mentality we have, we like this job. Kids like to wear the gloves.
"It's a sign if at this age you are already a goalkeeper in the Bundesliga. I saw his way, from a very, very bad start at Mainz when nobody really wanted him, to an outstanding goalkeeper.
"That's what I was interested in. I spoke to him, then took him, that's what we got - he's a really good goalkeeper."