The install option for SF4 was for all intents and purposes mandatory unless you like waiting seconds in between matches.
When I play old fighting games off of disc today the load times are as infuriating as they were back during the PS1 days.
What's funny is that the DD versions of PS1 fighting games like SFA2 and KoF99 STILL have the CD load times despite being installed on HDD!
A 50GB install would be a bit much though. Figure a lot of the data on a 50GB game disc would be redundant data anyway, strategically placed throughout the disc to optimize load times.
By next generation, consoles may well go full install disc like PCs, only using the install disc as a copy protection measure.