Hello! As the title says, I've been thinking about creating a video game based off a favorite game of mine. For anyone who's played Dragon's Dogma, it's that. Would it be easier to create a campaign since video games have the combat, plot, and characters all mapped out? Would it be wise to just copy and paste almost, if not everything from said game into Pathfinder?
Or should I make a campaign loosely based off various western RPG's? from things like Oblivion, Fallout, Dark Souls, etc etc?
Core Pathfinder often doesn't do well for video game/anime type campaigns. The most glaring issue is magic, video games typically use something that would be essentially be a spell point system (you can look up Psionic on the D20pfsrd to see what that looks like). And melee characters tend to be very unlike those in the games, even video game "fighters" have what would essentially be magic abilities. Something like Path of War (also on D20pfsrd) might be a better fit for you.
You'd have to make up rules from climbing on enemies, if nothing else.
And would you be trying to replicate the classes too?
Probably the easiest (and probably most effective) thing to do is use the SETTING, and then normal Pathfinder rules with some minor tweaks.
I'd cheer you on for Dragon's Dogma. Capcom only need to add more personality to that game.
Just add the names and settings using PFs rules and its just as good. The big difference would be the Arisen and Pawn system but pretty sure there are analogs too like the Arisen being the Mythic and Pawns supporting PCs.
"I wish you Pawns were as obedient as before."
"And we wish you knew to use your swift actions without being prompted."
The sadness happens when someone makes a spinoff tabletop and it just fails...
Dragon Age made me want to cry as did ASoIaF. At least Wheel of Time actually had the gumption to depower everyone across the board and make magic fraught with peril a la WarhammerFRP.
Scaling enemies shouldn't be too difficult, every time you beat them at the grapple checks, your character just moves to a more advantageous position on 'em to not be hit, deal more damage, or set the enemy up for a buddy. Us small species have been living that life yo'
I think it is best to make up your own Homebrew setting but letting it be inspired by the games you mentioned.
Trying to copy an existing setting and plot (especially from a different more linear medium like a video game or movie) might turn out very differently from what you intend it to be. Don't expect your players to follow the intended plot too much, they often want to go on their own adventures, and can be very unpredictable.
It's okay to build a campaign based upon existing games, because it helps in generating a setting quickly, but I would advise you to at the very least change the names of places, creatures and people. If players recognize the games and start drawing the parallel with the Pathfinder world, it invites them to start metagaming.