1. Sir Matt Busby
Matt Busby is mostly remembered for his managerial achievements whilst at United between 1945 and 1969, where he built two title-winning sides either side of the Munich tragedy in 1958, with the latter going on to secure the European Cup in 68. The success of his era has since been surpassed by what Alex Fergusons generation has achieved, but theres no doubting that Busby provided the platform for the United that we see today. Busby actually played for City before the Second World War, winning the F.A. Cup with them in 1934, before moving onto another of Uniteds arch-rivals, Liverpool. When the war broke out, like many other professionals, he played sporadically for various clubs, whilst also coaching an army team. At the end of the conflict, he went straight from the army to Old Trafford and paved the way for the next generation of managers, by demanding full control of the clubs transfers and coaching policies even managing to negotiate a lengthier contract in the process. The rest, as they say, is history. However, there are two incidents which could have resulted in Busby and United only remaining acquaintances and nothing more. On his return from the war, Liverpool were keen to offer him a return to the club and a stepping-stone into management as their Assistant Manager, but Busby wasnt so keen. Had he not been craving total control over affairs, Sir Matt Busby Way could now be an adjacent street of Anfield instead. For the point which relates to how City helped to shape Uniteds fortunes, you have to go back to the start of Busbys playing career in the late 1920s. His mother had applied to emigrate to America with her son, but in the nine-month wait for processing, he began playing football in Stirlingshire and after being approached by the Blues, opted to move to Manchester instead of the States. Perhaps another club would have come calling if City hadnt, but theres still a great possibility that if they didnt make their move, then all the above could be rendered redundant and void as Sir Matt Busby would have gone on to live a very different life indeed.