I thought I covered something similar before but can do it again.
It varies game by game.
Sometimes games will have an internal mode that allows you to skip it. I remember an N64 game (Forsaken) where if you waited until after some dev credits, press reset and then you could skip the considerably long intro. Various things like this exist, and also exist such that you might be able to tickle them with cheats (has already seen, died and does not have to watch again sort o thing).
If playing ROM hacker (in this case the very basics by opening the iso up and looking at the files inside) you have several more options.
On the basic side of things you want to take a look at all the video files and delete them. Sometimes it will work, sometimes it will crash. Beyond that find the smallest one, or indeed shortest one if that is a different thing*, that works (sometimes a really small one exists for credits or something but only works on that) and copy-paste however many times is necessary over the other files such that only the short one plays. Better hackers here will relink the files to save a bit more space (30 times 50 megs rather than 160 or whatever still amounts to a notable amount of space compared to 1 lot of 50 megs) but it will still be the same length of video. Some might look at other games (don't know what Sony provides or was the de facto chosen format offhand for the PS3) and see if they have even smaller files still, or the SDK got leaked you might be able to encode a frame of nothing and call that a valid video.
Sometimes you can chop down the file somewhat in a hex editor or equivalent and the game will run out of file and return to the game. Other times it will crash if you do that.
Sometimes you will find the file length/runtime or an end of file marker in the file itself and be able to edit that so it plays but stops after a few frames.
Beyond that we get into big boy ROM hacking where you alter the game's own code to either allow you to skip, load only a second/single frame or never load the thing in the first place. This is also how a lot of the cheats to skip things get made, though sometimes you get lucky and find a flag in a comparison.
*file size is proportional to length but 5 minutes of a black wall or talking heads will probably be less data than a few minutes of intense action.
