If you're looking for a good balance of price and performance for 1440p gaming, I'd recommend the AMD Ryzen 7 7600X. I recently upgraded to this CPU myself and have been very happy with it. It handles everything I throw at it smoothly at 1440p. Just make sure you pair it with a decent B650 motherboard and some fast DDR5 RAM.

AMD Ryzen 7 7800X3D

For Intel CPU, I think best choice is Intel Core i7-14700K.

The "best" CPU depends on your budget and the types of games you play. For competitive esports titles, a high-clocking CPU like the Core i5-14600K or Ryzen 5 7600X will deliver super high frame rates. For more graphically intensive AAA games, a CPU with more cores like the i7-14700K or Ryzen 7 7700X may provide a smoother experience, especially if you do other CPU-heavy tasks while gaming like streaming or recording.

Now you can get the new released Ryzen 7 9700X.

The new released 7600X3D is another great choice.

Remember, at 1440p, your GPU choice will have a more significant impact on gaming performance than your CPU. Pair any of these CPUs with a strong GPU (like an RTX 4060 Ti or better), and you'll have a great 1440p gaming experience.