Depends on the game. Anything that is fast paced. Racing/shooter/action etc. Should always have good framerate.
Everything that is slower like a turn based RPG or RTS game can have 30 FPS or even lower as long as it does NOT have a bad impact on the gameplay.
There is nothing more important to a game than gameplay.
But there is only 1 correct answer which would be.
Give me a "720p60 or 1080p30" option in the graphics settings.