It does depend on the definition of success. At Academy and Reserve level the team is less important - it's all boils down to finding a few individuals (if lucky) who might progress to the first team. I'd trade all the reserve and youth trophies for a guarantee of producing one first teamer every year.
That's not to say that City and Chelsea are more successful in that respect either. In fact they've been conspicuously unsuccessful. Just making the point that success at lower levels does us no good unless we can unearth those few key stars.