after 5 games you get to choose between nike and jordan
for your own signature sure, it's no set amount of games but it does take a while depending on how good of a player you are. from what I've played, you gotta play at least some of the games instead of skipping them, and in those games do pretty good. also try to get MVP, make all star teams, win the championship, reach some of the HOF goals, etc. basically I think the game is looking for you to be a nba "star" and it needs you to achieve some stuff before it unlocks the signature shoes. sometimes it takes a while for me, but I usually get the signature shoe in season 2 or 3, depending on how good my stats are and if the team is winning. good luk!