At launch, Super Smash Bros. Ultimate will have a total of 74 playable fighters. However, most of them will need to be unlocked. Fans can rest assured that it won’t take too long to unlock everyone:
According to Nintendo, it will only take a few hours (give or take) to unlock all the characters and it happens very fast. I think people were worried it would take 20 hours to unlock Bowser for example but this is not the case.
Source: Stealth @Stealth40k