Lets imagine a Minecraft.
The gpu has to imagine this large world in 3 Dimension. The larger, more detailed a world is the work the cpu has to do just for it to breath or run. Not to mention tracking when ur about to get hit and starting and stopping various animations. The issues with the gpu mainly have to do if 3d polygons have to many shapes to keep up with. Or various light and shine and glow effects.
Then lets say you are playing a 2D game like an arcade fighter spawning many enemies, spark effects and etc or plants vs Zombies. While being 2D is very simple for gpus of today, depending on how much is going on a cheap cpu can still lag if theres so many enemies, sparks, or projectiles to track.
Is there a genre thats most likely to always run smooth on a mid or lownend gpu and cpu. Yes. Simple puzzle games. Like Wordle or some spelling game. Or even bejeweled.
When the cpu isnt having to track so much of a made up imagined world, or level the cpu can focus all or most its resources to the game logic itself.
Lets say you are playing a simple touch crossword game. The ram stores the image and the lines but then the cpu only has to calculate when and where you start connecting dots. I realise that whatever graphics a gpu can give is imaginary while the most real thing is the actual cpu work/logic.
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