>>719260690 (OP)
>coding
>story
>art
>beta testing
>graphic engine
>devkit (source material and hardware to test it on)
But mainly it depends on the genre and the scale of your project, you can make a pixelated indie game or a game with sprites or 2d jpgs, you can make a nes/snes/ds castlevania, you can make an og DOOM, you can make a touhou game, you can make a halo, you can make an elden ring they all need diffetent approaches but first and foremost you need someone good with math and code that will do the basis or find a way to bypass that using an engine or something but even there what your end product will be will determine what you need and wether you can use certain tools or not.
For example oblivion/morrowind/skyrim/fallout or dark souls/elden ring required a big effort at the start but now that they've done the big of the workload they can just stand on what they've already done and be halfway there, see the duskbloods for example or starfield.
It also depends on how much manpower you have access to, the myth of the lone coder in his dark room that writes code for 10 years straight 24 hours per day is indeed a myth that only the funko pop audience believes.