I would pretty much consider myself as close to an expert on Superman as I've come across. I've read and own so many comics and collections and crossover events, etc that I've lost count. And my readings go back to Action #1 (reprints of course) so I'm familiar with most incarnations of the character. From your question I take it you are asking about the typical incarnation in the books and leaving out movies, animation, etc. So let's leave it at the books.
Typically speaking, in every version of Superman, he's been the upper limit or near upper limit of the comic book genre at that given time. NOTE: I'm speaking of the conventional characters and not the cosmic or force of nature personified types like Highfather or the Spectre or Watcher or Living Tribunal, etc. So what I mean is even though the original 1939 version would PALE in comparison to even John Byrne's man of steel version, he was the most powerful at that time.
The "ultimate" version of Superman would be (no, not pre-crisis Supes but...) Superman One Million. This version is basically nigh-omnipotent after living in solitude inside the sun for 15,000 years.
The version that is most powerful following thay would be Pre-Crisis Superman. This is the one that became the canonical version that everyone, even those who never read a Superman comic book knows. Even though Julie Schwartz brought this version down a few notches he could still pretty much tow planets behind him no problem (literally).
John Bryne DRASTICALLY reduced the Post-Crisis Superman's power levels during his time with the character and this is where it gets confusing when referencing feats of strength or limits.
The main takeaway here is that pretty mich everything Byrne did to Superman has been either eliminated or retconned away. And that includes both good & bad. Ever since Byrne left there has been almost a mandate to gradually increase Superman's power levels to something closer to his pre-crisis levels.
Superman say over the last decade is once again one of the most powerful characters in comics.
Superman's vision powers, even today, are absolutely mind-boggling.
His telescopic vision can see the edge of the galaxy (Lois says this in conversation with him). He can also see in 4 dimensional space (Final Crisis: Superman Beyond). We only see in 3.
He can absolutely see at the dna level and actually beyond that.
He not only can scan 20 miles for a person in seconds, this is really him taking his time to do it. In a recent issue, when Lois gets shot covering a war on the other side of the PLANET he HEARS the interruption of her HEARTBEAT! And reaches her from METROPOLIS in about 2 seconds. He could have moved faster but it would have caused massive destruction to do so.
SPEED: Even the more recent versions of the character can reach speeds fast enough to break through the time barrier. Especially through flight.
STRENGTH: In "President Luthor" Clark is so upset at Luthor's ascent to the presidency that he cracks a moon of either saturn or jupiter in half with a punch. And that's an older reference now. Superman is back to what I call "planet pusher" level or close to it.
So I hope this helps categorize somewhat where Superman is typically. Minus an inconsistency here or there Superman is generally portrayed as one of, if not, the most powerful conventional superhero in the DC universe.