I would say more efficient graphics (60fps) rather than better graphics. In competitive gaming, nobody is playing on "Epic" settings ("Ultra" equivalent on Fortnite), there's too many shadows and so on. Most popular streamers that play competitive have most settings on low. In the end, console players have another slight disadvantage there since they have way more shadows than us on PC (unless they can disable them ?)
Also many top-down shooters and arguably most games played from a third-person perspective in general. >_>
Keyboard and mouse are best when playing from a first-person perspective or with a complex interface, or really any game where precisely clicking on things is important. Thankfully there are lots of control options available for PC games though.
Agree with CryoBurner - 3rd person games where camera control and character control needs to be analogue is far FAR superior on a pad with two analogue thumb sticks. as are fighting games, racing games, side/vertical/twin stick shooters, platform games...
Of course 1st person games, RTS, or any game that requires a vast amount of inputs will be infinitely better on a kb/mouse.