Nearly overwhelmed by numbers when taking on the Enforcers, but clearly stronger, but still not so strong that they aren't a threat to him -

And later that issue, clearly not anywhere near the strength level of the Hulk (or presumably any of Marvel's other big boys - Thor, Hercules, the Thing or Namor) -

Early on they probably had him at about the same level as Giant-Man, but he was still having trouble with characters like the Kingpin and Man Mountain Marko.

What made Spider-Man interesting to me as a kid was how he wasn't the most powerful but he could think his way out of situations even when his opponent was more powerful (the Rhino, John Jameson in the Jupiter suit, etc.)

I also recall Spider-Man catching colds and being sick enough that his powers were affected. Oddly enough, this common man frailty added to the character’s appeal.

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I wonder if the injuries and illnesses having fallen out of favor was product of the character being represented in multiple titles, and a reluctance to tie other creators to a storyline presented in one title. While unfortunate, it would certainly be understandable if that were the reason.

By Marvel's peak (around 1966) after the Galactus Trilogy and the Silver Surfer was introduced - when the Marvel landscape wasn't yet over-crowded with "smartest" and "strongest" characters - I'd have to rank the strongest Marvel heroes this way -

Hulk

Hercules

Thor

Namor (peak conditions)

Thing

Silver Surfer (not utilizing the Power Cosmic)

Iron Man (normal conditions)

Giant-Man/Goliath (at peak strength)

Spider-Man

The Thing and Spider-Man have both had their strength levels bumped up over the years.  And from the late 1960s on we seem to have gotten a lot of characters who had super strenth - the Vision, the Valkyrie, Thundra, Adam Warlock, Charlie-27, Doc Samson, etc. and Spider-Man got pushed further and further down the list.  Wonder Man, who debuted (briefly) early on, would be somewhere between Namor and Thor.