I think we're possibly being a bit too critical of Rocky Balboa as a fighter, simply because the fights in Rocky films do not in any way accord with how boxing fights go down in reality. In reality, professional boxers are adept at avoiding or at least reducing the impact of blows - they don't hang their heads out goofily to be hammered by absurdly telegraphed head shots
Yes, to anyone who has seen a boxing match, at least the first few Balboa films make him look like, technically, the worst boxer imaginable. However, that's not a reflection of how good Balboa is supposed to be in his fictional universe. It's only the first film which makes him out to be Chuck Wepner, a gutsy, over-the-hill, talented guy whose talents have been wasted, who nonetheless impresses against a Muhammad Ali-level fighter. Subsequent films make him out to be the world's best heavyweight - destructive in II, skilled in III, superhuman in IV.
In the Rocky fictional universe, which has among other implausibilities basically Terminator-level AI, Balboa is supposed to be a legendary fighter, who can take down obvious Muhammad Ali stand-in Apollo Creed, and Ivan Drago, whose punches are about three times as powerful as any actual living human fighter can dish out.
Given that this is supposed to take place in a boxing ring, I think we'd have to assume that Balboa's (apparently) great skills would be formidable against most human-level opponents. It's a slightly bizarre notion, but this means I think that he can beat someone like "real Jackie Chan", because while Jackie Chan is a good martial artist and Stallone is not, Rocky is supposed to be at the pinnacle of boxing greats, even though he might actually look slow and wholly without technique.
My view? He can probably get up to Matrix, but no further, cos Matrix is truly absurd.