Opinions based purely on the Old versions of the game; nothing beyond 2

Given they have access to chi abilities, they'd at least rank along the lines of Iron Fist, since most of them only get one expression of said ability; a haduken, for instance, or Blanca's bio-electric shock, along with internal passive increases to strength and durability, agility, (the Flying Spin Kick thing) or even Dhalsim's elongated limbs.

If Cap and BP sit in the 5/6 range outta ten based purely on skill and combat aptitude, I would judge most of the street fighters in the 3-4 range. Zangief, DJ and my boy E. Honda, for instance, wouldn't rate very highly beyond the practical uses of their fight skills, while I would put people like Vega, Guile and Sagat solidly at 4s since they are "professional" street fighters, while the true masters, like Ken and Ryu, Chun-li, Dhalsim, I would rate at 4.9-5s.

I like to use real-world logic as much as possible when making these kinds of comparisons: Ryu is widely considered the best fighter in the Street Fighter universe, and his whole life is dedicated to honing his abilities. Because it's not really possible to train more than Ryu does, that puts him right up there alongside Iron Fist, Daredevil, Shang-Chi and Batman for me. He's in that elite company.

Assuming this is just taking just video game canon into account, the world Street Fighter exists in has folks like Akuma who casually is capable of punching an island and the island dies, sinking into the water. Akuma can meditate on the ocean floor, then Shoryuken a passing submarine, before shooting up past the water surface. Iron Man once blew up a mountain the size of Manhattan Island, for comparison.

Ryu can lift a boulder clear over his head, demonstrating considerable super strength.

Zangief discovered his spinning version of the Pro-Wrestling Piledriver by getting sucked into a cyclone while shoot-training by tussling with Russian Ussuri bears. The same Spinning Piledriver would be used on Yokozuna Sumo champion E. Honda to smash M Bison's ridiculous Psycho Driver fuck-off land-based laser. Honda could also survive being SPD'd from orbit.

Chun-Li could stop a speeding car with her Kikosho and police-worked the shit out of a global eco-terrorist group until it collapsed.

Dhalsim can levitate, teleport, and read minds, this should easily put him alongside the Mutant telepath community or with Dr. Strange's Sanctum Sanctorium

Balrog, or 'Boxer' to you tournament players, can kill a South Asian elephant with a single blow and smash a speeding car's engine with an overhand right.

Gill possesses cryogenic and pyrokinetic abilities, and can revive himself from near death.

The general population centers of Street Fighter, like Metro City, are riddled with sociopaths beating each other senseless for Zenny (currency), swag, and hopefully some training with a member from the game's active roster.

Street Fighter is really silly, but limiting them to just 'street level' is also silly.

Not to mention that, unless they changed it, part of Zangief's origin was they he used to wrestle bears

Well we know for sure Chun Li is capable of defeating the likes of Kingpin since we see her take him down in her MVC3 arcade ending